Okay, it seems kind of kitschy but the combo comes in handy when you return to the game 7 weeks into a short age.
As HA it does it's job very well. The undead's enhanced offense specialists and mighty 11 offensive point elites compliment the warriors offense modifying bonuses wonderfully.
Many players would get that right away but also the undead/warrior eliminates the need for both farms (undead) and potentially eliminates the need for training grounds (warrior). By most standards of play this provides the province with 18-23% of building space (that is assuming -8% farms and -10-15% for training grounds).
Personally, I find the versatility in what can be done with the extra acres refreshingly pragmatic. I used the excess acres to build and maintain about 20% barracks (in and ouy of wars) providing me with reasonable swift armies. Which is well because you need to plunder and abduct constantly to keep up development (being nonrouge undead).
Though I opted out of it, due to the before mentioned acreage the combo could be pretty easily made into an nonmystic A/M as well. I didn't do that this time for obvious reasons.
I hope that someone finds these thoughts on undead/warrior helpful some day. Players have their preferences, so I will forgo boring you all with the specifics of my "build strat" (I have a few modes with this one).