Frostseeker is absolutely viable. You want to generate as many crits as possible to tight groups of enemies (like pulled together by Pull of Eora or assembled around a tank.
Helwalker will work (Lightning Strikes, Duality:INT, MIG, Enduring Dance), Cipher (Borrowed Instincts, Phantom Foes, Eyestrike), Rogue, too (the crit AoE profits from Sneak Attack and Deathblows). Even Fighter (Devoted, Disciplined Strikes) is doable. Paladin will get +20 ACC on Flames of Devotion with the Ring of Focused Flames which will also help with crits (and Zealous Focus, too). Eternal Devotion also works with the Frostseeker AoE I believe.
An Arcane Archer can pull crowds together by himself (Imbue:Eora) but it's maybe best to leave that part to a wizard who can cast simultaneously and just keep firing arrows. Also Frostseeker will omit two of the three projectiles if used with Imbue shots which is a bit lame imo.
Even a SC Ranger is nice. With Twinned Shots and Driving Flight you are producing up to 12 hit rolls per shot which is pretty great in combination with Avenging Storm (from Heaven's Cacophony or scroll).
Highest ACC you'll get with Ranger/Cipher if I'm not mistaken. The frost AoE also generates a lot of focus.