Finished my second run through on Brutal difficulty. With a few choice solos and a good zerg strategy even the RTS portions were not terribly difficult. I can see how there may be a great deal of frustration for gamers not familiar with the genre.
My advice for folks, don't bother yourself too much with individual unit orders. There's only a couple points in the game where it really seems necessary. Other than that, keep your entire force together, send them at a tower, fire up the Druid Plow an try to draw off the enemy units.
It wasn't until my second play through that I even realized I could summon the Deuce in the strategy sections. That's basically a game changer.
Played some multiplayer practice rounds last night. The AI scales up to fairly difficult fairly quickly. I played probably 6 games on Normal AI difficulty and lost all 6 of them. One of them in only 3 minutes.