How is Timestop OP?
My problem with Timestop is that it creates scenarios that can pretty much play only one way.
Assuming... Assuming... Assuming... assuming... presumably...
Lots of assumptions and presumptions in your argument.
Edit: Okay, sorry for being bitchy... Trying to think of something constructive. See, my problem with making spells more in line with the PnP counterpart is the fact that so much spell utility is lost from the translation of a tabletop game to a realtime video game. There are a lot of creative ways to deploy a spell in tabletop roleplaying (DM willing) that are simply not possible in a game like this (unless a DM is supervising I suppose). I suspect that is partly why the Bioware interpretation of this spell is more offensive, we already had good spells to use for defense instead. With the proposed changes, I don't see the point. If you want to load up on cloud spells to assassinate a high level monster, or a PC, there is a good chance you will be spent afterward. That doesn't seem very practical to me.
In terms of defense, there isn't much reason to use it instead of Greater Sanctuary other than the fact you could buff up with some spells instead of fleeing.
Maybe this is a crazy idea, I'm sure this has been suggested and dismissed before... What if the timestop spell was altered to include players near the caster so they could prepare as well? Then it becomes an anti-ambush type of spell where everyone gets the chance to buff up. Would that be considered too powerful (or difficult to script)? I think the PnP version of this spell is pretty weak. Let's make it a spell that benefits the party and not just the mage. Rogues could use the time to setup some traps. Fighters and Archers could get into position and use any potions they need. Clerics could use whatever short-term spells they want and prepare for the worst, maybe even buy them some extra time to cross the map and save someone's life, etc.