Worth it, defense stacking and phalanx game is very popular at the moment so any bit of AOE is useful. (partially why risen moga is also amazing atm). It's also an attack which can get around stuff like protection, dodging abilities, arrow eater. It just in general is a really great choice without even going into the fact that when you're also running vengeful on him he has limitless upscaling damage.
Pretty much what Macca said -- Frost Cone gets better in proportion to how much focus you place on keeping Serkan alive and growing with Vengeful. If you just want a cheaper Vengeful Serkan to include as a ranged option and for the occasional games where he can grow out of control, then Weary/Cripple is fine; if you want to use a super-champ module with Ed and BCS to get a big fat Serkan, Frost Cone is much better.