Note that Chain Lightning can hit your allies as well, but it's a powerful spell and I use it all the time. Early on in Act II armor values tend to be fairly low, so using it can backfire relatively easily. But later on the Chain Lightning doesn't make much of a difference to hit an ally (plus it's thematic), especially with proper planning (I presume I'm not the only person initiating combat on my own terms?)
Burning and Necrofire haven't proven to be all that punishing imo, so I say spread it around. For a Lone Wolf none of this matters anyway. Bleed Fire is only "useless" because it takes a memory slot. If it were a free bonus for someone whose entire theme revolves around setting fire to everything, it's thematic and appropriate, not to mention convenient.
The only time I was genuinely averse to spreading fire was against the fire slugs very early on in Act I. Otherwise, I welcome pretty much all environmental effects as they help me kill things and can be used to self-buff. Surrounded by oil? Oily Carapace. Forgot to put nails in your shoes? Cryotherapy. Just don't feel like walking through that mess? Throw Dust. And then just in case things get really hairy, there is Cleanse Wounds. Not to mention the source-based Flaming Skin and the like, which grant invulnerability and grant Bleed Fire anyway.
I'm not saying that every character is going to want it or use it, but that should be implied since every character isn't going to run 10 points into Pyro or Aero.
