am I the only one who finds marle basically useless,gamewise?really,she never helped.oh well...
I think most proponents of Marle bring up the Haste spell, but I've always thought that by the time she Hastes everyone, I'd have already done enough damage with a non-Marle team to have done as well or better than with Marle (who has to rely on Double Techs to really do a respectable amount of damage anyways)...People against her commonly bring up Haste Helms which make up for the time it takes to cast Haste and you get a team with higher damaging Techs.
As for Double Cure, brought up by teaflower, when I actually need to heal everyone, I don't like to have to wait for two separate people's gauges to fill up...plus, if you have one person who can heal the whole party (Robo's the best choice for that), you can focus on offense at the same time with the other party members...
It can sort of just come down to how you play...