With the defaults of per_replica_batch=1, seq=2048 and gen_len=512, a completion takes about 20 seconds.

I'm not sure yet what settings I'll end up with if I decide to play with this more. per_replica_batch=3, seq=1024, gen_len=64 would give an experience roughly similar to the AI Dungeon that I'm used to, though less clever than the Dragon model, and a bit slower at about 10 seconds per batch.