The weirdboy can be a very powerfull and often overlooked HQ choise, especially at low points costs. But to take him for a specific role is exactly the opposite of how to play the weirdboy imo. For a good look of how one can play out for you , check out this guide from the boot camp sticky :-
http://www.40konline.com/index.php?topic=130950.msg2105104#msg2105104I have an unbeaten 1k list featuring a Warphead, 90 boys(nob,pk,bp), 7x lootas, 2 grotzooka kanz, and da green barron, its a highly recommmended list for a fun game but also very competative. Just dont expect a quick game
In this setup my anti-tank will be primarily da barron, with lootas for lighter AV. If that fails, the kans and nobs are both capable, and 30 boys can glance AV10 to death too. The warphead sits with 30 of the boys (shootas) and does whatever he likes, just dont deploy him in the middle of the squad, use 1 or 2 boys to keep coherency and put him right at the front