DS costs 45 RP, so if you had max RP you can dump 2 before you have to use other abilities.
So, on the condition that: At the start of your burst, you have full RP, and the target has less than 70% HP, you’ll have 2 very hard hits. With DRW, that’s a nice burst, but it isn’t going to eat through heals and bring someone from 70% to dead, and still have uptime to switch targets to keep pressure.
The current meta is also very fast paced and bursty, which means you’re going to have a hard enough time getting to max RP, and getting your target to 70% before you even begin your burst.
Does Blood’s DS hit harder than Obliterate? Yes. Does this mean it’s going to do better in PvP? No.
During PoF you can rotate and land 5+ Oblit frost damage crits. Combine this with the 5 Frost Strikes, remorseless winter, Abom’s limb (I know Blood has this too, don’t worry),Chill Streak, and that you’re starting it from a stun and Frost’s burst is overwhelmingly better. If matches lasted longer, and there was better CC in our toolkit, Blood would stand a chance of being ~B tier.
You also have to factor in that there’s no comp that could presently accommodate Blood’s needs. You need someone else to put enough pressure while you build up for your burst, while being survivable enough to last while you do it, and they also have to provide a setup that benefits you. I really can’t think of a class that could provide that sort of setup.
Additionally, running Death’s Certainty is nice, but using DC essentially means a DS that didn’t land. And, there’s no mechanic that promises a DS crit, which means you’d need to do a full crit build. Even if you did a full crit build, and had, say 30% crit, statistically both of your DS during your 8s burst window are not both going to crit to clutch it. If they do, great, you might down one, and be able to rotate to the next, but if/when they don’t, which the majority of the time they will not, or if you’re not able to down them from that, you’re looking at another 2min to setup again, and you honestly probably won’t survive until then.