Burgh has two level 22 Pokemon and a level 24 Pokemon, so Darumaka at the low 20s should be able to wreck overall :P Apart from Dwebble with Smack Down...
Anyway in regards to training places for Burgh, I'd probably try the Relic Passage in Castelia Sewers, as it has a couple different Pokemon, most ranging from level 16-18. Castelia Garden also has Pokemon from level 15 - 18.
Additionally, if you havn't done so you can go to the Battle Company;
>The building just to the west of where you start (to the west of the Pokemon Center) is the
Battle Company. On floors 47 and 55 there are various trainers to vs, which can provide good EXP if you havn't done so already.
Additionally, you can try the Game Freak HQ
>The first building on the right is the Game Freak HQ. Castelia Street (Eastern Street)
There you can battle Morimoto and Nishino (3 level 14 Pokemon with Morimoto and Nishino has a level 16)