If you're serious about a TP-draining area-of effect style buff, please consider making a variety of effects that DNC can bestow this way.
Potential Enhancements to Consider
1.) Regain
2.) Critical Hit Rate + Critical Attack Bonus
3.) Double Attack Rate + Triple Attack Rate
4.) Other? Something defensive? Probably won't get used.
Originally, I suggested:
Backup Dance (Dancer level 95, Recast 5 minutes, duration 5 minutes or until the DNC has 0 TP). Sacrifices TP to regenerate surrounding Party members' TP. ---Consumes 100 TP to give the dancer a "Sphere" effect that drains the DNC's TP by 2/tic to give party members a 2TP/tic regain effect as long as they are nearby.
Instead, make this a new category of dance, like Sambas, and increase DNC's ability to support the party similar to the manner in which BRD+COR are able to enhance the party. Consider, however, that this will constantly drain the DNC's TP so the effect should be fairly potent to make up for it. And yes, they should stack with sambas.
Category: Backup Dances
1.)
Rousing Cheer (DNC Level 92)
Grants the effect of "Cheer." Party members in a 10' radius receive the effect of Regain. Drains 2/TP tic from the DNC, and part members regenerate 2TP/Tic. The cost of this ability is set less than the others because the DNC will see no benefit from this ability.
2.)
Tenacious Cheer (DNC Level 95)
Grants the effect of "Cheer." Party members in a 10' radius receive a boost to critical hit rate and critical attack bonus (including the DNC). Drains 3 TP/tic. This should be at least 5% each, but I think 10% is more fair for the cost. Still significantly weaker than Blood Rage, which is intentional.
3.)
Frenzied Cheer (DNC Level 99)
Grants the effect of "Cheer." Party members in a 10' radius receive a boost to their double and triple attack rates. Drains 4-5/tic. 10% double attack and 5% triple attack.
Balance the ability by making it wear off if TP reaches 0 and give it a somewhat long recast (3-5 minutes?). You can even make it not have any effect when solo if that's a balancing issue you're worried about.