To finish Juggernaut bestiary the best is of course "Jug seal" (Apocalypse seal), but as team of 400-550 lvls you have to be very careful (your hunts may be quite dangerous) and be aware, that your exp/h won't be good. You won't have speed boost there, so running from pack to pack will take more time, than it should.
Better exp/h you'll make on Prison. Sounds funny, but after recent changes (nerfes and buffs) it's true.
Juggernauts seal on INQ... well, if you want to make bestiary from other seals at the same time, you can choose it (as well as POI), but I wouldn't consider it if you want only Juggernauts.