I have the Perma-Alliance with the Orks and it worked well for several Shards.

Now..i have to defend my homeworld, oncemore :),...and..i can build all Orkbuildings and hire Orks...but if i enter a Orkprovince i get the "old" Offer Alliance, fight or run Options.

I was really happy as i had seen the Map because a part from the 2. Ring where Orkprovinces and then they formed a "path" of 2X3 provinces with Mithril, Iron&Marbel...so i happly aimed directly for the Orks after conquering the the connecting province from the 1. Ring...and...barly escaped :)..because they didn't remember that we where allies^^

Even if you have an alliance, orcs would look for hero's power - they wouldn't join to weakling.
Thing is, open resource adds +1 to effective ring, and orcs in second ring with resource would have Ogre, third ring with resource can have Cyclop / Giant.
If you don't have comparable army, they would attack you.

Ahh...riddle solved...they indeed had Ogres as i found out several Turns later.

Many Thanks :)