It is not clear cut about might being the best.
All skeleton damage calcs done using this excel spreadsheet. This sheet does them all correctly and you can plug in the auras and skill levels, which I did.
For the to hit calcs, skells have the same level as you do at the time of summoning. If you are L50, they are L50 with. If you assume 20/20 on RS and SM, then they have an AR of 605. A NM balrog is L55 with 869 defense.
%ChanceToHit = 200 * AR / (AR + DR) * alvl / (alvl + dlvl)
AR = Attacker's AR
DR = Defender's DR
alvl = Attacker's level
dlvl = Defender's level
So with the above you have 200 * 605/(605+869) * 50/(50+55) = 39%
That is pretty horrible. A L12 blessed Aim gives you +240% to your AR. (I use L12 because an L50 Blessed Aim merc hired in Normal, and you always want to hire in normal, has an L12 aura, see This AB thread for details) That would put the AR of the skells up to 2057 and put the chance to hit at 67%. Which is a significant improvement.
That AR will become even more important if the level difference is even greater than that. So I think a skellmancer is better served by more AR tthan by more damage.
Let's look at some average damage calcs. Skellies do 124-127 damage at 20/20 (125.5 average). And you have 8 of them. So a rough calc, without any mercs will get you: 125.5 * 8 * 0.39 = 391.56 in a rough per swing averaged over all your skellies.
With the Blessed Aim merc you get this: 125.5 * 8 * 0.67 = 672.68
An L50 might merc has a L8 might aura. That adds +110% damage. Of course with the way auras and skeletons work (base damage) * (raise skel enhanced damage + other enhanced damage) that only takes the damage to 187-190 (188.5 average). So you get: 188.5 * 8 * 0.39 = 588.12
So you do much better with a blessed aim merc at L50. Nearly an average of 100 points of damage.
Of course that is for late NM. Lets look at Hell. You will probably be 70 at the start and around 85 when you kill Baal, though it can certainly be done earlier than that. I am just looking at where you will be if you just play through the game with an average of 3 other people in the game most of the time.
Hell Fallen are L67 with 933 defense, so you have them beat on the monster level curve if you enter Hell at L70 (and we will assume the merc is always the same level as you). Lets also kick the skeletons up to 30/30 for raise and mastery. That has your skeletons doing 309-312 damage (310.5 average) with an AR of 905.
Base to hit them becomes: 200 * 905/(905+933) * 70/(70+67) = 50.3%
A L70 Might merc has a L13 Might aura. That gives +160% damage. Which only takes your skeleton damage up to 480-484 (482 average). A L70 BA merc (hired in normal of course) has a L16 aura, which gives 300% to AR. That should kick the AR of the skeletons up to 905 + (905*3) = 3620.
The to hit percentage then kicks up to: 200 * 3620/(3620+933) * 70/(70+67) = 81.2%
Average damage per swing calcs (30/30 gives you 12 skeletons):
Might: 482 * 0.503 * 12 = 2910.3 (or for one skel take out the factor of 12 and it is a simple to calc 242.5)
BA: 310.5 * 0.812 * 12 = 3027.3 (or for one skel 252.2).
So things aren't quite as good for BA there, but that has you in front of the monster level curve.
Lets go to the start of Act 5. Put you at L80. Take an Enslaved (L79, 1546 DR). Blessed Aim aura to L18 (best a merc can do and 330% AR boost). Might is at L16 and +190% damage. Skipping the detail.
Might side: 514.4 * 0.371 * 12 = 2294 (191 single)
Blessed Aim side: 310.5 * 0.720 * 12 = 2683 (223 single)
Now Baal. You L85, Might L17 (+200%). Baal L99, 2847 DR.
Might side: 525.5 * 0.222 *12 = 1405 (117.1 single)
BA side: 310.5 * 0.533 * 12 = 1988 (165.6 single)
Most of the cases are going to look like this. Getting more AR for the skellies is usually going to be be better for you. Though I didn't take into account Amp Damage/Decrepify and that does start to make some differences as well.
Thorns is also a very viable aura to look at as well. Amp and Decrepify can knock physical immunity off most things and it also helps mages and revives deliver damage back. I haven't look at it all real closely but there is a strong case for it being the best choice as well.
EDIT: Dang it, I didn't consider area levels... That change the calcs I do believe, but I don't think the results will change that much. The skinny looks to be that the farther ahead of the mlvl curve you get, the better might looks to be. There are some other subtlities but I too tired to do any more right now.
All skeleton damage calcs done using this excel spreadsheet. This sheet does them all correctly and you can plug in the auras and skill levels, which I did.
For the to hit calcs, skells have the same level as you do at the time of summoning. If you are L50, they are L50 with. If you assume 20/20 on RS and SM, then they have an AR of 605. A NM balrog is L55 with 869 defense.
%ChanceToHit = 200 * AR / (AR + DR) * alvl / (alvl + dlvl)
AR = Attacker's AR
DR = Defender's DR
alvl = Attacker's level
dlvl = Defender's level
So with the above you have 200 * 605/(605+869) * 50/(50+55) = 39%
That is pretty horrible. A L12 blessed Aim gives you +240% to your AR. (I use L12 because an L50 Blessed Aim merc hired in Normal, and you always want to hire in normal, has an L12 aura, see This AB thread for details) That would put the AR of the skells up to 2057 and put the chance to hit at 67%. Which is a significant improvement.
That AR will become even more important if the level difference is even greater than that. So I think a skellmancer is better served by more AR tthan by more damage.
Let's look at some average damage calcs. Skellies do 124-127 damage at 20/20 (125.5 average). And you have 8 of them. So a rough calc, without any mercs will get you: 125.5 * 8 * 0.39 = 391.56 in a rough per swing averaged over all your skellies.
With the Blessed Aim merc you get this: 125.5 * 8 * 0.67 = 672.68
An L50 might merc has a L8 might aura. That adds +110% damage. Of course with the way auras and skeletons work (base damage) * (raise skel enhanced damage + other enhanced damage) that only takes the damage to 187-190 (188.5 average). So you get: 188.5 * 8 * 0.39 = 588.12
So you do much better with a blessed aim merc at L50. Nearly an average of 100 points of damage.
Of course that is for late NM. Lets look at Hell. You will probably be 70 at the start and around 85 when you kill Baal, though it can certainly be done earlier than that. I am just looking at where you will be if you just play through the game with an average of 3 other people in the game most of the time.
Hell Fallen are L67 with 933 defense, so you have them beat on the monster level curve if you enter Hell at L70 (and we will assume the merc is always the same level as you). Lets also kick the skeletons up to 30/30 for raise and mastery. That has your skeletons doing 309-312 damage (310.5 average) with an AR of 905.
Base to hit them becomes: 200 * 905/(905+933) * 70/(70+67) = 50.3%
A L70 Might merc has a L13 Might aura. That gives +160% damage. Which only takes your skeleton damage up to 480-484 (482 average). A L70 BA merc (hired in normal of course) has a L16 aura, which gives 300% to AR. That should kick the AR of the skeletons up to 905 + (905*3) = 3620.
The to hit percentage then kicks up to: 200 * 3620/(3620+933) * 70/(70+67) = 81.2%
Average damage per swing calcs (30/30 gives you 12 skeletons):
Might: 482 * 0.503 * 12 = 2910.3 (or for one skel take out the factor of 12 and it is a simple to calc 242.5)
BA: 310.5 * 0.812 * 12 = 3027.3 (or for one skel 252.2).
So things aren't quite as good for BA there, but that has you in front of the monster level curve.
Lets go to the start of Act 5. Put you at L80. Take an Enslaved (L79, 1546 DR). Blessed Aim aura to L18 (best a merc can do and 330% AR boost). Might is at L16 and +190% damage. Skipping the detail.
Might side: 514.4 * 0.371 * 12 = 2294 (191 single)
Blessed Aim side: 310.5 * 0.720 * 12 = 2683 (223 single)
Now Baal. You L85, Might L17 (+200%). Baal L99, 2847 DR.
Might side: 525.5 * 0.222 *12 = 1405 (117.1 single)
BA side: 310.5 * 0.533 * 12 = 1988 (165.6 single)
Most of the cases are going to look like this. Getting more AR for the skellies is usually going to be be better for you. Though I didn't take into account Amp Damage/Decrepify and that does start to make some differences as well.
Thorns is also a very viable aura to look at as well. Amp and Decrepify can knock physical immunity off most things and it also helps mages and revives deliver damage back. I haven't look at it all real closely but there is a strong case for it being the best choice as well.
EDIT: Dang it, I didn't consider area levels... That change the calcs I do believe, but I don't think the results will change that much. The skinny looks to be that the farther ahead of the mlvl curve you get, the better might looks to be. There are some other subtlities but I too tired to do any more right now.
---
It's all just zeroes and ones and duct tape in the end.
It's all just zeroes and ones and duct tape in the end.