QUOTE(varst @ Oct 19 2011, 21:07)

Thus you don't need to further decrease the amount of damage you receive. Which means you don't need poison, slow, weaken, blind.
But poison doesn't just halve their SP/MP regen, decreasing their damage output (or rather, decreasing your SP usage), but it also decreases their evasion, making you little less likely to miss with your spells.
And it also does damage.
Damage which can be quite considerable, if the monster lives for a while.
The damage increases with the base HP of the target, so a legendary should get some extra damage from it.
And poison lasts a very long time, and doesn't cost that much to cast.
Over time, that damage adds up, and if it goes it's full duration, I doubt there are many spells that can compare to it when it comes to damage/mp.
QUOTE((Cheater) Tiap @ Oct 19 2011, 21:27)

I still think Weaken is worth casting.
Nerf = 1.25 damage bonus at 20 base cost
Nerf + Weaken = 1.25*1.1 = 1.375 damage bonus at 30 base cost
If you can spare mana for Nerf chances are you can do the same for Weaken.
Plus, more chances to proc Coalesced Mana.
Personally, I stopped using any debuff at all.
Killing a Legendary on Normal takes me 4-5 Pestilences right now, it feels like a waste spending two turns for spells I don't really need.
I'd rather use them to try and steal some mana.
Except that weaken only decreases their physical defense, which does nothing for mages. And he already established that you can survive their damage.
Or did you mean bewilder?
But seriously, doesn't weaken work?
After all, it halves their physical damage output.
Which means you can replace regen2 with regen1, which heals less per round but actually costs less mana per turn (but has to be recast more often, but that allows you to let your HP drop a bit between recasting if you are going on plus).