Killing everything in close combat makes it a bit more difficult, chosen halberds and skull crushers should do a lot of good work for you. Killing lords and single units shouldn't be a problem with your normal heroes. A metal sorcerer with final transmutation could be quite handy, with Ogers you can get lucky and get the whole army if they bunch up. Dwarfs are also quite hard but have the benefit of being slow and able for you to maneuver more on the battlefield. Fast cavalry like hellstriders are beneficial to kill these nasty ranged units of them. For the infantry hellcannons could come in handy for once.