Quick questions about The Feast

[EnigmaticDodo]

..........

[BloodRubyXII]

just play dancer and win mate x

On a serious note, that's not how debuff stacking works.
Easiest to learn dancer, monk, ninja, red mage, summoner, bard
Nothing to watch out for in a week every melee above plat will be SAM or NIN and every range will be dancer.
Get boxes, kill people, don't drop your medals that's about it.
Watch Brian's feast guide.

[Tachion]

Debuff stacking is multiplicative, not additive, so it's even more than you think. For example, feint(25%) and phantom dart(20%) end up being +50% additional damage taken from the melee rather than 45%. You have the right idea though that people try to line up big bursts for the best chance at securing kills.
At the moment I think only Scholar is significantly undertuned. The rest of the jobs are all playable.