FoW is super easy to clear with Heroes, you can just take a standard team and churn through, I do it regularly.
UW i've never gotten around to clearing, I don't really like the area so I get bored about half way, only real hard part is the Horsemen quest. Will do all in one go one day
Urgoz/Deep, are both quite difficult, i've only ever done them with a full team (or close enough to a full team). They probably heroable, but how easy it would be... no idea.
Killing Mallyx you can do with all Heroes, and is amazingly easy if you take a conset. Take lots of spirits, earthbind works great for knock locking, take PI Mesmers for lots of group KD, imbagons are super, strap on DwG, and take pure heal WoH monk. Remember no enchants/hexes/conditions, rely on spirits/shouts/wells/pure heals to keep you up. Hardest part is when the large group of Dreamriders and the sodding Dryders turn up about half way through, make sure your heroes are spread out and you focus fire. If you get past those the rest are super easy, and Mallyx wont know what hit him
As for armor, the EotN armor sets are the cheapest to buy if you already have Luxon/Kurz and Vabbian.