As we're dumping counters on our opponents creatures all over the place I think
willbreaker could be pretty strong.
Cast it, move to combat, Volrath's ability triggers and you steal a creature.
I know I'm gonna be running it!
Infected Vermin or
Crypt Rats can work really well if you fiddle the stack.
Activate 'Vol-rat's' ability to deal the damage, hold priority and switch him to an infect creature.
-1/-1 for everyone!
Than you have your pick of the creatures
Champion of Lambholt I think is a must include as well.
Builds it's own stock of counters and immediately makes you field completely unblockable to all but the biggest creatures if at all when copied by volrath.
What do we think of creatures like
Spawnwrithe?
Volrath copies it but gains the copy ability and becomes a 7/5 and keep the copying ability, which means when he dealt damage the legend rule doesn't apply and you end up with a ton of Spawnwrithes which also have Volrath's ability to copy the best thing on the board.
But theoretically would never change back into Volrath and would always return to being souped up spawnwrithes
...Thinking about it the same works for copies.
Activate Volrath's ability targeting something non-legendary, then
clone him and you effectively have two Volraths without breaking the legend rule