1) Get a crystal Wand (u will still get bonus aoe from gloves)
2) Get Javelin skill and the node with +60% damage on judgement. It's super good for boss. You hit stronger, heal and tank (Flag mode) and you don't need to specialise in shield rush skill to use it.
3) Get the Hammer&Anvil 5/5 in Forge Guard. +25% tanky for map, +25% damage for boss. Use it with Javelin when needed.
4) Eventually at some point in late game, i take shield bash and perma stun bosses (get full duration stun & cooldown recovery, go look for them, always fun to stun lock bosses) and like you said, sigil isn't really important here.
5) ultra end game : Julra Ring with Healing effectiveness/elemental damage overtime to kill every boss in less than 10sec (or attunement for funny aoe xD)