Honestly, this was easy. I was able to complete the map within a few weeks.
Killing the stack of Rakshasas is a joke. With raise dead and phantom forces you shouldn't take serious losses and by the time you engage them, you should have more than enough units to take them out. There are undead all over markal's side of the island. Grab them all. Get some units from your base, engage the rakshasa. (you should have about 200-300 skeleton archers by this point. I don't remember exact numbers.) Once they're dead, take the stack of wraiths behind them. This map is over from here.
Put isabel in the sanctuary south of her base, so when the mage hero shows up, he won't crush her and cause you to fail the mission, by the way.
Once you take godric's sister, just focus on raising your wraiths. The AI will (usually) focus on attacking them, and the wraiths have more than enough attack power to kill the angels in the ambush. If you exit this fight with any losses, you fail at raise dead.
After that's over, go straight to Godric.
The godric fight can be tricky relying on a single unit. Just keep your number of wraiths up and focus on the titans first, and then go down the line to next strongest monster, and next strongest monster, and so on and so forth. The fight will get exponentially easier with each major hitter you take down. When the haven troops pop up, don't sweat it, they should be much easier to crush than the mage troops were, and you should still have a full stack of wraiths.
This fight is even EASIER if you were able to build wights/wraiths at your base beforehand.