WoW newbie looking for advice

[Klaus]

PW:S is preferable to PS because you could end up with other mobs being involved. Likewise, more often then not you will kill the mob and still have some of your PW:S left for the next mob. Another thing to consider about why PS would be a worse choice, fear breaks much, much easier now on damage, I rarely see a PS last to full length now even with low amounts of damage.
The problem with putting a non-DoT ahead of a DoT is you lose the effect of the first Shadoweaving Debuff, this is why DoTs go up first, to increase damage output. Applying the DoTs will give you 1 go 2 Shadoweave debuffs on the mob before your first DD hits, thus giving that DD an additional 2% to 4% damage. Putting the DD in first means it gets no additional benefit as the Shadoweaving is applied after the spell hits the target.
Some yes, but the benefit of PW:S is it in all likelihood, you may still have some of it left when you finish off one mob to move onto another. Also, unlike Affliction Warlocks with their Yo-yo pulling, Shadow Priests do not have the same amount of health and do not have the ability to drop multiple VEs quickly where as a Warlock is dropping Siphon Life on every mob. Trying to Yo-yo pull as a Shadow Priest is dangerous and leads to more downtime than a Warlock would see (the Warlocks typically are spending their downtime picking up loot as they're already near full health and mana when the Yo-yo pulling finishes while a Shadow Priest would be low in health and mana).
Seems everyone ignored the part where I said sub 50. You always start with DoTs when you have Shadoweaving because it gives you more Shadoweaving debuffs on the mob before you hit with the DD spells. Also, VE is not a damage spell and does not apply Shadoweaving debuffs to the mobs.
No, it is always preferable to start with a DoT once you have Shadoweaving to maximize your damage and your efficiency, especially later in the game while soloing. SW:P and VT should also be the first two spells cast once you get to 50 with VT going first.

I understand the point, but the problem is once you have Shadoweaving and VE, you're much better casting SW:P, VE, and then Mind Blast or Mind Flay as the mob comes in and using a wand. The thing is that people may also be forgetting here as you level, you want to make sure that for the last 5 seconds the mob is alive that you are not casting spells, either letting the DoTs kill the mob or wanding it down so you're outside the 5 second rule and therefore Spirit Tap is working at maximum effectiveness to get your mana back up.
As I stated above, the reason for the DoTs first is always to get Shadoweaving started to get maximum effective damage. Starting with the DoTs get your 1 to 2 free stacks of Shadoweaving which is very useful.

Also, I have seen plenty of PuG tanks that a single Mind Blast after they're made an attack lose the mob. As such, it's better to be prepared for that eventuality than to not.

I think we're going to have to agree to disagree. I find that PWS is a big waste of mana in almost any situation, and using it leads to more downtime than anything else I can do. I also find that the "lost" damage from not getting shadow vul. up for the mind blast is more than offset by the use of the "out of combat" cast time at the start of the pull. Finally, if you can't learn to play differently in a group than you do solo, you have larger issues than your spell rotation.

Of course, after level 50, I start with VT to get the out-of-combat cast time, and that's a dot, which fits with your theory. However, I almost never use mind blast except on tough mobs, because I find that to be the 2nd biggest mana hog leading to downtime. If the dots and the wand are going to kill it before I'm too low on health, I'll let them do it because it's mana already spent. If I want to speed it up a bit, I'll sometimes add SWD to finish them off (but this is rare because SWD is expensive, too). I do look to see if I need new buffs (inner fire, fort) and try to cast them before the dots kill the target so as not to completely disrupt the spirit tap (waiting the 15secs for tap to expire is better, but I'm not that patient).

Hmm. Now that I think about it, there's a mechanic to Spirit Tap that I'll need to go explicitly test for myself. My impression has always been that the instant you get a tap, you go to full out-of-5-second rule regen with double spirit. If you then cast a spell during the tap, it drops to half. Your assertion is that it will go to half if you've cast a spell within the last 5 seconds before a tap. I'm also going to check to see if VE applies shadow weaving, because I know it stacks the Darmoon Card (crusader) and I thought it stacked weaving, but I'm not positive. Funny how you can play a class for years and not recall these things, isn't it? :)