She definitely will, her base plant dmg at LV18 is too much if they land...what, 3 hits? That, plus the actual skills plus the 50% AS bonus from her ultimate make her plenty strong. Not to mention 20% passive CDR and 3s CD on Q, all you have to build is grail/rylai and you got yourself a winner.
Hadn't played Gragas all week long, love his ultimate for pushing people away from drake/nashor and stealing buffs