I understand why folks think its a bad idea. If there are a lot of blue decks, specificly tempo decks like delver or stoneblade variants then the inclusion of Deathrite is pretty huge. The same thing is true for reanimator and dredge decks, if there are a lot of them in your meta then the dethrites will be great. Otherwise it's just a glorified lavaman. I have had some sucsess in the mirror by gaining a lot of life with them, but that is ofsett by the PoP my opponents are playing. But I tend to try and play around that as much as I can so I end up gaining more then I lose.It sounds like your taking on so much extra risk for such minimal gain... don't get me wrong I like 2c or 3c burn in some formats like modern but that is mainly because we're lacking in quality burn spells.
You can look at it like this:
3 Lavamen + 1 Fireblast -> 4 Deathrite
1 Sulfuric Vortex + 3 Searing Blaze -> 4 Tyrant's Choice
1 Sulfuric Vortex -> Sylvan Library
Lands -> Lands
The difference between our decks is that yours is better against creature decks like Elves ect, while mine has a better MU against Tempo and graveyard decks. We are both able to deal damage at the same rate, but I get access to 1 more mana every turn and can cast more spells. Different strengths for different meta's. And mine if filled with GY decks and U/x/x tempo decks so I prefer the 3c setup I'm running right now because of it