Unlike many I actually think HoMM III is one of the bad HoMM games. It's overbalanced and mightheroes became WAY too strong!
I guess if you don't have any high level spells or masteries, this is true, but well set up magic heroes absolutely wreck might heroes unless you have that magic cancelling item. Implosion melts things, prayer gives you the stats to match a might hero on top of haste, dimension door is dimension door, resurrection becomes true resurrection, and berserk wipes out entire armies. If you've got the masteries for the spells, you're a HoMM2 caster on steroids, might has no chance against mass slow's that cost a few mana, etc. Going up against a fire/water/earth/air master just means everyone is crippled unless you have mass dispell or antimagic.
5 had some good ideas, but it also had those mind blowingly stupid ones, like putting hero casting into the turn order and making how fucked you were entirely a matter of who goes when. It had potential, lots of it, but it was crippled by stupid, much like 4 was with heroes being free kills, until they got powerful enough to be the whole army themselves.
Where is HoMM / Ubi sitting on their nasty DRM these days? Don't remember which HoMM I canceled buying when they had the uproar over their DRM, but really haven't checked them out at all since then. Still present, not as bad, worse?
They went to Uplay, which is rife with problems and causes much screaming. They're not as anal, but they're still a disaster.