Archon is fairly good support for Pyromancer, some +fire damage at the bottom leading into benefits for critting, which pyro wants to do a lot of anyway.
For the first 30 levels or so, Elementalist isn't bad for your third soul, though I'd probably not bother putting any points into it (your Archon points are generally going to be better for the time period you're using Elementalist). After about level 30 your lesser elemental pet stops gaining levels through ranks and therefore stops scaling with the things you're fighting. After that you probably want to do something like 10 points in warlock for Opportunity or maybe some points in Dominator for some CC utility, but it's really up to you where you go from there, and by the time you get there you'll probably have a pretty good idea of how things work
If random outcomes aren't acceptable to you, then don't play with random people.