Orcs are stable, but a bit tricky. They are slower and weaker than undead (but stronger than almost everything else). So keeping people in position is important.
And here is where I disagree with you on Orcs, I'll grant you that they are only a little bit faster than Dwarfs, so definitely are on the slow side, but weaker than Undead? No way.
True, they only have a stupid Troll with ST 5 compared to 2 Mummies, but Bobs have natural Access to Strength
and General skills, which imo makes them the stronger team, since they can get Guard as well as Block and MB. Mummies need a double for block.
Also Orc linemen are only marginally more expensive than Zombies or Skeletons but are faster (ok 1 MV is not that much faster, but for comparison's sake) and have 1 AV more, which makes them way more resilient than most other linemen.
Another reason why Orcs are stronger or at least on par with Undead is that they have a thrower, Sure Hands from the get go is a godsend with AG 3 and gives you a passing option; not a reliable one mind you, but in a pinch this has saved my butt on more than one occasion.
Finally, Blitzers all have Block; a big advantage especiall early on and the whole team is dirt cheap compared to Undead, one dead or severely crippled Mummy early on and you are going to be struggling the whole season instead of only maybe 1-2 games.
All in all, I think Orcs are at least as strong as Undead as a starting team.
(And now having listed all that I am seriously thinking about playing Orcs next season, I miss those greenskinned bastards)