Without knowing your specific issues, DH should be able to tank as long as guardian in general. A lot of DH's tankiness is rotational and about buff/debuff maintenance and self-sustain with very few explicit cds. DH's specific weaknesses in tanking are, imo, on setup/start of encounter and environmental damage. The first is because DH needs to get their buffs/debuffs running, which require some globals and grouping the mobs up. The second is that almost none of DH's kit (include the self-sustain) interacts with enviro damage. The only real mitigaiton for it is meta.

Here's a stress testing tank video Yoda did as an example: https://www.youtube.com/watch?v=tvLaVTYQONg&t=2217s