Sometimes it may as well be beneficial, on the other hand - e.g. playing as paladin MC in final fight with act1 hag you just can't chose power without consequences... so when another party member converses instead, you can benefit.
For most purposes I consider all companions as equals - they share the same problem, so when you decide to play dumb/mean MC and let the usual talking to e.g. Wyll, I do not see why MC should be autoselected to talk after fight. Maybe binding it to party position might be an option.
