Vitiate's most used attack during combat is lightning, and Talzin was capable of handling Sidious's lightning, which is more potent than Vitiate's, so she has the advantage in the force. Plus she's a skilled enough duelist to hold her own against Windu, someone who is second to Yoda in an era that Lucas considers as the prime of the jedi order.
The wraths are outnumbered by powerhouses.