"Is each of the paths viable and fun?" That's what we should be asking, rather than comparing different styles/choices in some eternal (infernal) competition. Flavor/variety has its cost, and I believe no dev can be creative and so different in options while having everything equal out--equality leads to blandness, and that's only important if pvp is front-and-center. I have so far won--or was going to win when I stopped playing--using ever combo I could think of, though the melee-only route was in trouble due to some tactical errors and a bad starting position. Some paths are clearly more powerful than others--is that a terrible thing, really? Does that break the game in some people's opinion or am I missing something (like sarcasm)? Yes, balancing things way out of line is important, but if we talk about OP and nerfing too much, we'll sound like the MMO crowd.
For the beastmaster path, I think it's balanced that your leader has to take a beating while taming them (a wrestling of wills, kinda), and you have to baby them along (tactics is important early on because so many of the ones you can get before level 5 are so fragile). But as you begin building up your armies of beasts, your kingdom/empire power climbs without your maintenance costs soaring, and before the end, the other factions are paying you to keep your hordes off of them. Could my beasties withstand a powerful assault by a higher level AI using more expensive groups? Probably not. But man, it's fun to play Tarzan.