Captured Tempered Jho in 15 minutes with dual blades. Many traps, flash pods, and buffs were used. It seemed like I was doing really good constant damage too (and I barely got hit unless I had on Rocksteady Mantle), he just eats a LOT of hits and his weak spot is hard to reach while he's enraged. Well, that's the case for Dual Blades at least. I tried with safer weapons that I'm not as good with and it took way longer. I even used a Gunlance for the first time in this game just for kicks and it took me 30 minutes to capture I had no idea what I was doing but didn't cart! Lances are good with defense I suppose.
I actually just got a Tempered Kirin quest that was 15 minutes long and had 5 attempts. I think my best bet is to use a Fire Greatsword and I ran out of time 3/5 times. The other 2 runs I finished in about 12:30 and 14:00. Both times I carted at the start for a Fortify buff, otherwise I probably would have run out of time again. The ranged weapons are good against Kirin so I should probably get on learning those if I happen to get another quest with a 15 minute time limit.