I don't think that Vergil sucks, however, it's weaker then Dante.
The reason is that Vergil mobility is not "fluid" like Dante's and Dante have more weapons and tricks.
His teleport dodges are quite flashy but have too much recovery frames and you are exposed to enemy attacks!
But I think that is more fun to use then Dante and he has some fun moves.
It's quite essential to learn some basic jump canceling to expand Vergil's combat abilities.