Like it, but I would swap the Runemaster on foot for another Runesmiter (on foot), for tunnelling a unit of 10 (merging 5+5) Auric Hearthguard, so in your turn of choice: emerge from tunnelling in 12" range from a monster, Lofnir command ability in your shooting phase, 20 magamapike ranged attacks +1 hit +1 wound --> [dmg 2 each] monster killer!! Nice tactic, already used, very satisfiying (for you, not really for your opponent...). Obviously you can't take the battalion. But in that way, you have room for at least flame-spitter and infernoth. Also the wall would be usuful, droths can cross it without penalty...
Need a bit of testing, I think