Saeviomagy said:
Having the spell force balancing with a DC equal to the save DC would be a far more coherent way of handling things.
It would, however, also be substantially more powerful. Everyone has Reflex saves. Not everyone has Balance ranks. A forced Balance check of 15 or so is much harder to make for most characters and monsters than a Reflex save of 15 or so.
Finally - I don't really think that having a 1st level spell allow sneak attacks and loss of dex to ac for what will usually amount to a SINGLE round, and only then IF the target doesn't have 5 ranks in balance is overpowering.
You're not the first to say this about a single round, and I just dont get it. I use
grease fairly often with my primary PC, and I (a) usually use it on Large creatures (b) who are unable to move out of the effect. It's not at all a difficult situation to achieve. I would
love for it to deny Dex, setting the two rogues up for sneak attacks, but IMO it's just too powerful that way. As is, it's a very good first-level spell.
Also note that there's
no way for the target to avoid the huge tactical disadvantage being imposed on him by the "no Dex" ruling. (Aside from having 5 ranks in Balance, and who's going to cast the spell at a thief-acrobat?) Apparently, even if he makes his save, y'all would deny him Dex.
Compare with something like summon monster or colour spray...
Summoned creatures can sometimes be worked around, and
color spray has limits on hit dice affected. Not to mention that
grease has substantial effects aside from the "no Dex" side-effect y'all wanna give it, whereas the other two spells you mentioned are pretty much specifically
intended to have that effect.