Lion stance is not enough.
Kraken stance is also pretty weak, and you need invest points into other stances to boosts its damage, and finally to boost if even further you need "-enemy all resist" which is very difficult to stack on gear.
One option is to use rebound, it has 50% conversion to magic. But it can be annoying to use, for someone used to stampede.
Another option is.. merc. Abjurer kills immunes really fast, even if you don't support him with protectors or/and elemental totem, as on more merc support dedicated build.
But to make abjurer good, you need to optimize its gear.
- get him to energy factor bonus cap (calculate based on energy/ef, all info is in docs)
- stack -135% enemy lightning resist
- Make sure all items that can have +skills (crystal sword +3, chest +2, amulet black dwarf with extra +supernova and so on)
- reach last 5fpa cast speed superbeast breakpoint (requires quite lot of fcr)
- rest - focus on buff duration to extend superbeast, you can fit about 200% buff, on top of stats mentioned above
With these stats, merc becomes true beast, and it can literally solo ubers at decent speed, if you just spirit walk around with no minions and never even use your own throwing skills.