Interestingly my DK / SHM / Destro * 3 had no trash problems. In fact I had zero issues until I hit the last boss of the instance. Holy shit did that rip my heart out. I tried for like 2-3 hours to get it and it just boiled down to the mobility issues of the warlock and the fact you needed interrupts in that phase. Sure I could just respec them but it agitated me so much I rage quit.