[Rockabye]

If they're going for an invocation it'll most likely be telegraphed by Charge Mind (since invocations and even spells themselves tend to be lackluster without it). Once they use Charge Mind, the possibility of them preparing for a chain cast go out the window, since they'll be locked out of using it until Charge Mind wears off. For them to get in a full spell combo they will already need to be in range (since movement could take away up to 3 of their casts, leaving them with only 2 after activating Chain Cast, and that's -if- and only if HSDW is active), and for it to be every basic Evoker spell they would need to be directly linear to their target.

More likely than not these are not going to be all rank 5 spells (though they could gear their character that way if they wanted to sacrifice the passive damage bonuses and invocations, but in that case they would be a gimmick character with no other options). Let's also add in that unlike Charge Mind's damage bonus that's factored in before reductions, these will have resistances and RES applied to every cast, which can be a lot of damage reduction overall. This is topped off by things like Wraithguard and Devotion. You could say that Charge Mind is for the RES-based opponents, and Chain Cast is for the DEF-based opponents.

As far as the "all spells" things goes I agree with you, and I'll go ahead and change that.