It is much much more effective to have a maxed TK if you build a ES-sorceress.
16 hard points in TK improve the effectiveness of your ES by 100%.(6.25% each "hard point).
You should have gone with 1 ES and 20 TK. That's the proper way to do things. Start with 1 in ES, and 20 TK, since ES can be boosted by +skills to get to higher levels.
I hope it's not too late to remake your character if you have done this.
I said "if", meaning I haven't started yet
And this isn't really an ES sorc so to speak. I only have one hard point in each skill. It's the equipment that raises ES to lvl 27.