Have patience. New champs usually come off the PBE overpowered or underpowered. Riot lets the OP champs sit that way for a while so they can rack in the RP, then when sales of the new champs start to go down nerfs for them appear on the PBE.
Take
for example. He was blatantly powerful for months and Riot never batted an eyelash. Then when
all became the new hotness and Kench's sales went down, Riot hammered him with the nerf bat.
So if you're buying him because you like his kit, get him. If you're buying him because he's so powerful, don't expect that power to last more than a couple months before he gets reined in and toned down.