Going with the Hone Sundan was the correct choice. Baal dies just as quick, even though it's a more pesky fight. Mephisto just basically lays down and dies within 30 seconds, and that's with p7. I only put 1 Shael in it --- I need another Shael and an Amn still =x
Decided to progress to Hell to give it another try --- and to see if I do any better. I did do better, cleared the Den of Evil. Took some time, was scary for a moment (Corpsefiend would amp me, and being extra strong, he chunked about 800 life a hit). But, Ahsab and myself stood victorious.
I have more confidence about Hell than I did. Den of Evil gave me 11 million experience or so --- which seems like a p7 Baal run worth. Part of me feels like re-running it on P1 or P3 with MF gear, but I don't think that's a valuable use of my time. I'll probably run Mephisto a bunch more, then try to progress even more.
Encouraging, though. I saw a Hellforge Plate drop in the Den. I found a rare Stygian Pike, which is cool even though its stats sucked.