I think that at its current incarnation, Time Stop will still remain very much the key utility in wizards unleashing torrents of pain. And I say wizards, because the deadliest Time Stop combos will now mostly be in the hands of wizards who can afford to splash into spells like cloud kill, acid cloud, delayed blast fireball, etc, etc. Of course, sorcerers can take them, but it will come at a greater cost.
I do still believe it's a step in the right direction. But I don't think it's finished. If I'm reading this correctly, with 1d4+1 rounds of hasted spell casting, that's potentially 9-10 spells. On average, it's 5-6 spells. (Though I will say that I do very much like the randomness in its duration. That helps break up the bread-and-butter feel of wham bam Time Stop combos).
9 seconds is already a long time for a mage to do what he wants to. This would make it potentially.. 12-30 seconds? Out of just one casting?
While yes, it does stop a mage from using the easiest and most deadly combination of saveless spells, I think it's opened still for a lot of extremely deadly combinations. In short, while it's a step in the right direction, in its current form a clever wizard will have no trouble whatsoever emulating the damage of Time Stop + Isaacs Greater Missile Storm by layering AoE spells, and slowing movement (Or even Bigby Grappling) to keep them trapped inside the clouds for the second or two after the Time Stop collapses. It will look cooler, but it will be just as if not more deadly.
There are saves associated with a number of these AoE spells, and that makes it a huge difference. Evasion, fortitude saves. That's not something to be understated at all-- but I think if the goal was to try to make Timestop less offensive, that another hard look should be taken at the duration of the spell.
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Also, I'm a little disappointed in the language we've used to encourage or support these changes. Time Stop isn't abusive if it's legally attainable and used within the rules of PvP. It's overpowered. And while it might be overpowered, and while it might be good for the mage player to recognize that it's overpowered, as long as the rules are followed in engagements there's just no right to call it abusive. And the fault for its presence and use isn't with the player, but with the staff for the way it exists within the current balance. That isn't to trash the staff, I should say. It's instead to assert that a player using abilities and combinations that are legal in every aspect of the game is simply not abusive for using them.