You're feelings aren't very far off - Warmahordes is an extremely well balanced game. When I first started, I did hear people whining that "this faction is over powered" and "that faction is under-powered" from a few people online, but what I quickly came to realise is that every person had a different opinion of what was under or over powered - some thought Ret was overpowered, some underpowered, some thought Menoth was unbeatable, others said it was too soft, some thought Khardor couldn't possibly win, yet others thought they were impossible to crack. What it really was is that every army was fairly balanced, but players had troubles overcoming particular opponents using those lists.
I'd suggest you look at This Thread
which is a statistical analysis of games played during the 4 Templecon tournaments over in the USA - over 400 games, 160 players, and some representation by every army in the range.
What it found was that the "top" army won about 58% of it's games, the bottom army, about 43% of it's games - basically less than 8% difference either way, and within the margin of error.
Hell, when ever I've looked up tournament results, I've always been quite impressed that there's usually a good selection of winning factions - it's never top tier and bottom tier factions, it's all about the particular set of players who turn up, and what factions the good players fancy. Hell, look back through the results of major tourneys around, and you'll probably find every single faction has been in first place at some point in the recent past. No faction is left behind.
It's one of the really good things about this game, and PP way of releasing it - everything gets updated and refreshed all at once, no waiting years while your army slowly decays.