Yeah. Though I'd probably take another Relic even more suited to a Prince first: namely, the Black Mace. Yeah, you have to get stuck in for it to have an effect, but... on the other hand, a Prince without one hits like a mere MC, rather than a freight train of pain. And a Heldrake is markedly cheaper for a higher-strength Torrent, even if it is harder to get a good cover save with and has some angles it needs to work on, now that it's 360 degree firing arc has been nerfed.
Yeah, Black Mace helps you take out Wraithknights and Riptides, but against basically everything else I've never seen it make a huge difference, and even with the Mace a Daemon Prince just isn't very good in combat; I think they're super good at picking off Devastators, IG Veterans, Windriders, Tactical Squads etc. but if you find a basic SM Dreadnought to be a seriously risky proposition, you're probably not a very good assault unit. Hell, even charging 10 Tacticals through terrain (because you can't kill most of them with the Brand before you charge) is going to cost you a embarrassing couple of wounds from Krak Grenades. Better to fly about the place picking off the weak with your BBoS and landing to keep up that kind of work against backfield support units than gun for something that can actually fight back. The Heldrake has a stronger shot and is cheaper, for sure, but a Heldrake's going to get maybe four rounds of shooting if it doesn't get shot at all. A Prince can shoot every turn of the game, and that's a pretty big deal, as well as being much tougher (mainly through being really small and easy to hide) when he's on the ground to assault/get objectives.
But yeah, CD DPs are generally better. Access to Greater Rewards for surivability, not having to take a crappy god-based psychic power... just about the only other edge for CSM DPs is the spell familiar. Well, that and the fact that the "Daemon of Nurgle" rule is worded slightly differently to give them defensive grenades in the CSM book, but talk about minute nit-picking, eh?
Infernal Tetrad, ho!