Noobish Questions (updated frequently)

[Skandranon]

At lvl 29, the highest arcane explosion does 60 damage. I'm not sure that's worthwhile.

It's better than nothing, which is precisely how much damage you'll be doing at close range otherwise. After you pop CoC and Fireblast, you can choose either doing nothing until they come back up, or having a no-cooldown, instant option to keep doing damage with. Proportionately, it'll inflict about half the damage of your fireblast, which is quite good.

The case for improved flamestrike is that there are very few talents in the game that reduce cooldown, and that the lower you reduce the cooldown, the more each fraction of cooldown reduction counts. In fact, the more points you put into improved fire blast, the greater the % cooldown reduction with each point. It's not quite as dramatic as having NO chance of getting arcane missles interupted, but I was somewhat under the impression that at least 30% of my damage in WSG would be coming from fire blast on the run. 5 points in fireblast reduces the total cooldown by 18.75%, upping the DPS of the spell respectively. That's better than the % improvement 5 points in improved fireball gives (14.29%).
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Theorycrafting. As Bob has said, you don't chaincast fireblasts in PvP. Fireblast's use comes in windows of opportunity between other stuff, and they are rarely exactly 6.5 seconds apart. Either the engagement is lightning-fast and finished in one blast, or demands of mobility will ensure that they're each separated by enough time for talented or non-talented fireblast to cool down.

Also, while DPS is more of a PvE statistic (burst damage is what matters in PvP) your percentages are misleading. Yes, Improved Fireblast is a bigger percentage-wise DPS increase, but that's +18.75% on a base of 14.3 DPS at 29, whereas improved fireball is +14.29% on a base of 46.5 DPS at the same level.