Does the E/Mo have any function other than tanking Dhuum, or does he just hang around until all the quests are done?
Actually yes, the E/Mo performs a few other critical roles.
1). Complete the Forgotten Vale 'Wrathful Spirits' quest with the SoS Rt/R. If you look at the ele build, you'll see a few fire damage spells along with burning speed.
A year ago I created this build to solo the Wrathful Spirits quest - which I could do in around 2 1/2 minutes. However, that was back when the quest only spawned 15 enemies, whereas now the quest spawns 3 waves of 15 for a total of 45 enemies. I can still solo the quest now - however it would take about 3 times longer. But with the Rit/R and a Summoning Stone (Ghastly Summoning Stone ftw

) the quest completes much faster.
In fact last night we pulled off a /age 10 completion of Wrathful Spirits, which was our fastest time to date
2). Kill the 3 enemies (skeles or silver terrorwebs, could be 3 of either or a mix of the two) which spawn at the back of Pits during the 'Imprisoned Spirits' quest. As with 1) above simply put up all enchantments; and once the first enemy spawns, spam skills and have the Rt/R summon spirits up near you and kill each enemy.
3). And for added laughs, at the start of 'Clear the Chamber', once all enemies are balled up/blocked by the A/Me and other permas, the E/Mo may also jump in and fire off his fire-damage spells and degen the mob with burning speed. There's a good chance he'll die if a dying nightmare is near, but that's not an issue as the Rt/R can quickly use 'Flesh of My Flesh' to rez the fallen E/Mo. The combination of the perma damage/degen spells, ele fire damage/degen spells, and EoE makes that mob drop incredibly quick
