Perfect IV Alakazam
I evolved a perfect IV Alakazam with Confusion / Shadow Ball...I'm really trying to justify powering it up since it has perfect IV'S and I like Alakazam in general. In mirror matches, Shadow Ball SHOULD be useful, right? Is this at least a decent defender? Is this worth powering up? Or should I just power up my 84.4 IV Alakazam with Phsyco Cut / Dazzling Dream (lvl 20)?

Answers
I wouldn't. I would hold onto him and wait and see if Ghost attacks become more useful in gen 2.
He's right at that CP Bubble too where he'll be too low to stay in gyms. Maybe they'll change the mechanics at some point to make more defenders relevant. Until then, he'll be below the main 6 defenders
Also, the way dmg is calculated right now having a non-STAB charge move is the kiss of death without massive stats to make up for it
Here's a quick and dirty comparison calculation:
- Assume that IVs make up 10% of the total stats of a pokemon (in Alakazam's case they're only 8%, but we'll ignore that cause it's easier to work with tens).
- Assume that ATK, DEF, and STA IVs all equally affect a pokemon's DPS.
- Thus, a 10% reduction in IVs = a 1% reduction in overall DPS.
In the case of a 84.4% IV, the reduction in DPS is about 1.6% compared to the 100% IV.
- Compare Confusion with Psycho Cut. Confusion's true DPS on a 100% mon = 17.22, whereas Psycho Cut's true DPS on a 84.4% mon is (21.05 * 98.4%) = 20.71.
Your Psycho Cut Alakazam is the better attacker.
When attacking, Psycho Cut deals more damage than confusion and is easier to use dodges.
For IV comparisons, given Alakazam's low base stamina and highest nonlegendary base attack, having higher defense and stamina IVs is probably more preferable. If your 84% has good Def and Stm IVs, then don't feel bad about powering it up.