Normally I'd agree with you, for those exact reasons, and my first prototypes were all generally flat (also being a fan of the Ultima series.) But when I tried

Normally I'd agree with you, for those exact reasons, and my first prototypes were all generally flat (also being a fan of the Ultima series.) But when I tried the current isometric style on a whim, it managed to solve all of the problems I was trying to address. Probably because I use a hybrid approach: only the underlying battlemat tiles are isometric. The miniatures are flat, slightly-transparent stand-ups and always face the player.