Yea it's hard to CC a DK with a trinket, desiccated ground, Icebound fortitude, and lichborne but it's easily kited and those spells have 2min CD and Icebound fortitude has 3min CD, forcing a DK to trinket is easy once they use them they are done for.
If you are playing a healer and a DK is popping his CDs that is the best time to kite and use defensives, because they will probably silence/stun, pop CDs, stack necrotic with blood tap and empowered rune weapon and finish you off with a soul reaper. When the DK is bursting just kite and use defensives and you will be fine.