The only ones that seem properly powered for being tier 10 perks are Pain Train and Concentrated Fire. Gun Fu particularly seems a little iffy, since you'd probably get better results with concentrated fire, combined with the other luck perks, like 4 Leaf Clover, Crit Banker, and Grim Reaper's Sprint. However, Nerd Rage and Ricochet seem like they would synergize well together. But the problem with Nerd Rage is that it's maxed out benefit conflicts with the perk as a whole.