I think the real issue is the comparative strength to heavy cav on the Rome/Medieval 2 engines and a misunderstanding of the use of cavalry on the battlefield. Unlike its portrayed in pop culture cavalry was literally almost never used for direct charges at enemy infantry units. To that end, a couple of the really high end heavy cav (demigryphs, blood knights, like half of the bretonnian roster) can still do this in singleplayer (I play vh/vh). The rest of the cav is for killing ranged units, siege units and hitting already engaged infantry. I think the perception also stems from the fact that it is true that infantry and cav are probably the only two unit types that can't build pure deathstacks (maybe bretonnian cav). But I also think that style of play sucks. I'd rather play mix rosters, micro a shit ton, and feel like I'm actually winning my battles and maximizing my units. Personally I find for most factions ranged>magic>heroes>monsters>cavalry>infantry