you really would be much better off if you just roll a PvP character. That way you have access to all the skills, all the weapon mods, and all the armor/runes/inscriptions. Plus you won't have to carry around a bunch of GvG crap on your PvE char...
The above is for domination; illusion skills (and hence illusion weapons) function somewhat differently, but the general concept is the same - cast speed mods tend to be only marginally useful as you already are reduced to around 2/3 cast times. The vast majority of illusion skills do not have long casting times as a balance tool either. The mainstay of illusion skills is degen and snaring - thing you want to be able to spam and spread as much as possible, hence making recharge the priority.
The equipment you should be using in PvE is practically the same anyway.
Also, use health armor.
So, in general;
Enchanting Set
Martial/Shield Set
Double Recharge set (dom/illu)
+60hp Staff if you want (dom/illu)
+energy set (dom, maybe insp, mainly for gales or getting off an insp +e spell when low energy)
niche sets (40% fast cast and double recharge, etc)