Xerxis seems pretty interesting. I'd play him. Of course unless he was flat awful i was going to play him because he's riding a giant Rhino! the mount is actually really good with knockdown or a pitch without having to roll a crit. the feat is cool, signs an portents all over the table, not having to worry about control area for one turn for a long range kill. Mobility + ignite + rush + feat is going to make Molik pretty sweet with him, but even on titans that is really good. Not sure what beast should be bonded to him, maybe just a krea so that he will always have that buff on.