I made a bullying build with Stamina Thief 5 and slugger 3 along partbreaker and my sleep horn, just to experiment. The problem is, i tend to focus on the monster's head and rarely get solid hits into the body. Exhaust triggers on anything else than the head, whereas Slugger builds up on the head only. This being said, this skill doesn't fit all playstyles, but i also experimented building up exhaust specifically, and the results are definitely there: tried it against the cheeky pest that is the black blos, in the arena, and last half of the fight he was suuuper slow and always drooling, he was literally moving in slo-motion even when digging or when coming out of the ground (i've never seen a diablos be so slow and de-energized and i'm not exagerating). My take on this: really comes in handy against super fast and spontaneous monsters, like barioth or viper tobi etc. , however the user should focus on getting hits on the body as to build up the exhaust. Hope this helps!