I want to preface this by saying yes, PvP definitely has a CC problem. However, this issue can be easily rectified by implementing diminishing returns, and plenty of more detailed threads are already discussing the situation.

Getting to the first topic, DRK in PvP is definitely a traditional tank - we have tons of mitigation tools and healing potential. However, tanks in PvP are meant to take on a support role, and this typically means having strong CC options to control the battlefield and suppress lethal threats for our party. Currently all DRK has is small draw-in effect and a paltry 3s bind on a 30s CD, which is laughably weak compared to PLD/WAR's ability to stun reliably on a 15s timer (WAR even gets a gap-closer attached to its stun too).

DRK needs to have a more flexible kit to effectively compete with its blue brethren. A meager 3s bind is often not enough to secure a game-changing play, and DRK isn't seen terribly much in higher competitive tiers for this reason alone. Possible solutions would be adding a 2s stun to Plunge, returning Unmend to its kit (as a CD with either a stun or the old draw in effect), or allowing Shadowbringer to apply heavy against targets hit to prevent enemies from disengaging/leaving DRK's patch of Salted Earth.

The second issue is arguably not as important, but still worth mentioning, which is DRK's poor ST damage potential. Tanks don't necessarily need to hit hard to be worth bringing to the team, but DRK's kit involves using their own HP to deal damage, which typically would mean DRK would cater to a risk/reward playstyle that favors aggressive plays to deal pressure against the enemy team. The "risk" is hovering at lower HP thresholds, which leaves the DRK vulnerable, and the "reward" should be a tank that could output higher than average damage to make securing a kill more reliable/practical for the job.

Admittedly, this is harder to balance since it deals with the battle formula and all that, but a good start would be upping Bloodspiller's minimum damage to 5000 (equal to that of Souleater), but letting it scale to a maximum of 16,000 as their HP drops. Bloodspiller doesn't feel terribly impactful at the moment, and only really makes a difference with paired with Eventide.