Exava actually doesn't do a thing for the deck. She doesn't give +1/+1 counters herself, and by the time they hae counters from Marchesa, they are already attacking so haste is irrelevant. She is good with unleash, but urabrask and anger are straight up better here. Thrumming bird may have potential.
It is true that Marton doesn't buff himself, and is a bit fragile; honestly he is a bit of a glass cannon. But that is why he is good in Marchesa: because it doesn't matter. He can be fragile. He still gets a +1/+1 counter for attacking (this triggering his ability). If they block and kill him so what? He has not only done his job, but he is coming back at eot. And of course @ 4 comic he is tutor able via fleshwrither.
There is always The drowned, but they are pretty terrible...scratch that. thought they were a dork, they aren't they just regenerate...