Now, from what I've seen in the runs, usually the tank selections are K/D
Yes, but unfortunately most K/D I see in random runs (outside DC) either can't hold aggro properly because K/D's overall aggro is worse than most other knights, or they can't keep Holy Flank running properly. And if a player can't do both, why playing K/D at all? However, if a player can play K/D properly, it should be one of the best choices for DC for sure.
As far as I can see, there are players who claim to be good, but at the moment I haven't seen a player in this class and I haven't seen one before. Why ?
Our tanks in my former guild and my current one play(ed) K/S very often, especially in DC and the blood arrow never was an issue, iirc you don't even need it to run permanently, you can toggle it on and off. But yes I agree, in random runs you see almost nobody tank with it, everyone only K/D without aggro or without up-time on holy flank
But K/S is a perfect beginner class for knights imo (decent aggro, huge range, even some basic utility and CC) and after mastering tanking with it, ppl could move on to K/D which deals less aggro but has better support if played properly. You see this behavior at many other tank classes: The more aggro / easier gameplay, the less support you will have on board. Example: Even K/M is viable, but has almost no useful support for the raid - but it's aggro is really good and it's easy to play through tons of aoe hits --> fast Threaten stacking and misses are not fatal for melees