As an alternative to kiting a rat ogre the entire match, if you do not kill the first set of normal (slave/clan) rats after you have dropped into the area with the barrels, the ogre will not spawn. You can and should however kill specials (gutter runner, packmaster, ratling gunner, stormvermin, globadier).
We ended up killing rats on the 7th/8th barrels in order to stay alive as well as spawn the ogre before we finished the level, but it may not be necessary to spawn the ogre in for the achievement - we just did not want to risk it.
Helpful traits include Devastating blow (push further), improved pommel (half cost pushes as well as a chance of it costing 0), improved guard (half cost blocks), second wind (chance of restoring stamina when block breaks), and perfect balance (1 extra shield of block) as well as the trinket that gives % move speed and removes dodge fatigue. Light weapons are recommended for easier dodging as well as shields for the extra stamina.