I think the wyvern is overhyped. It's better than the mortal team, of course. But it also eats up a heavy slot, which is infinitely more valuable. It's good against exactly one thing, masses of low armor infantry. You put that infantry in transports and you're golden. The wyvern is extremely specialized, and I dislike it for that reason. If you're not facing hordes of low armor infantry, it doesn't do jack ****. The manticore, in comparison, can fill multiple roles. It threatens higher armor, it instakills just about anything it hits due to ridiculous strength, and it's very good anti-vehicle as well as being anti-horde.