I agree with the others, ditch illusion. If you can't interrupt 1 second spells you shouldn't be trying, although I'm sure you can
I once spent a whole hour trying to master interrupting 3/4 second spells. I'm pretty much pro and interrupting healing touch now

mainly due to the fact that I made the enemy skill casting bar absolutely massive (THIS DEFINITELY MAKES INTERRUPTING EASIER).
The reason why there aren't many powerblock mesmers is because its a difficult build to play. Migrane + interrupting is much preferred because its easier. I have a mate who prefers powerblock to migrane but he's a great interrupt (he was jealous of my healing touch achievement). It is however a great skill. Used with diversion, blackout, possibly arcane thievery, shame etc etc. Power drain is great energy management and can always be guarenteed if you find an elemental. Power leak however is my favourite interrupt if not favourite skill and if you refer to the MoR post, its potency doubles with a 10 second recharge

- in my opinion.
For me, making a foe lose 26 energy with one skill which can be used every 10 seconds (MoR only) is just superb and better than powerblock with its long recharge time. The 15 second disable is great and could be used well in a certain build (e.g. a well thought out one).
I'll recommend some skills for you if your using power block, but if you think your good enough, try MoR/p.leak.
11 FC
16 Domination
9-10 Inspiration (can't remember)
Arcane Thievery
Diversion
Blackout
Shame
Power Block {E}
Power Leak
Drain Enchantment/Power Spike/Power Drain -- choice of energy management
Res
I would opt for power drain due to high energy requirement of this build (power block is 15 energy cost). And don't even attempt to be affective on a boon prot, stick to enemy healer monk.