My immediate thought is - buy some transports.
A Venom for the Wracks and a Raider for the Warriors would be helpful. Drop the Wracks to 4 and pack Urien in there. Or maybe two Raiders and don't drop a Wrack.
Also, as a general concept, if you want to run Urien, then you should probably be fielding more Coven units to take proper advantage of his special rules. I frankly think Urien is pretty 'meh' unless you specifically want to run his uber Grots, but even if you're not doing that, he is certainly of more help to the army if there are other Coven units for him to lob tokens at.