I'm primarily interested in Nagafen, PoH, PoF, Sky, Veeshan's Peek, and anything in Velious or Luclin.
Nagafen - cake, as mentioned already
PoH - could do Maestro for sure, but Innoruuk 2.0 (correct that Agnarr server has PoH 2.0 right?) is level 75. Would be quite difficult in group gear.
PoF - Terror and dracoliche easily. Fright and Dread you could do with an epic cleric + a devoted tank/ranger for chain rezzing and taking death touches. Or with decent dps just 1-2 sacrifices for DT's could probably be fine.
Sky - You could clear up through and including the Spiroc Lord on island 5. Again you'd need an epic cleric and a devoted taunter for death touches in order to kill Keeper of Souls, Overseer of Air, and Spiroc Lord. I really doubt you could do Bazzt Zzzt.
Veeshan's Peak - You could do all 6 dragons, but you'd need to be on your game. Need to be adept at positioning the dragons on corners, dancing around the corner to avoid their AE's, and a mana drainer to prevent them from gating is helpful. Hoshkar in particular can be tough.
Velious - easy stuff would include Zlandicar, Kelorek`Dar, Vindicator, Tormax, Statue, Yelinak, everything in Sleeper's Tomb except maybe Zeixshi-Kar the Ancient, East/West ToV, most of Plane of Growth except Ail the Elder and Tunare (and tbh I forget if any other minis silence besides Elder, so maybe watch out for that), Velketor the Sorceror, Wuoshi, all of Western Wastes including Sontalak and Klandicar. NToV dragons would be quite the slog, would take ages just to kill Aaryonar to access it. And some dragons would just be simply too difficult like Lord Vyemm and probably Feshlak. He might not be that bad with decently buffed fire/cold resists. AoW would be very doubtful.
Luclin - easy stuff would include evolved burrower, all of Akheva except maybe Shei, Thought Horror Overfiend, Grieg, Servitor of Luclin, Lcea Katta, Lord Seru if you have bane weapons and a cleric/shaman, Rhags 1 and 2, Arch Lich, Creator, and probably the first two Thall Va Xakras in Vex Thal. Some "maybes" would be like burrower parasite, Shei, High Priest in Ssra (I'm unsure if they fixed this event or if you can cheese the adds). Definitely can't do Emperor or Khati Sha, and probably not much of Vex Thal other than the two entrance Thalls.