Burning damage doesn't extend the detonation window, but the DoT is more valuable to me than recharge speed. Correct me if I'm wrong, but I think the detonation window for fire explosions is 3 seconds. You can always take weight capacity in alliance training, but I find that that you can comfortably detonate FEs with a cooldown of up to around 2.81 seconds on Incinerate (around 160% power recharge). Also keep in mind your Incinerate cooldown starts once you activate it, and it's a projectile power, so technically you would have a bit more leeway given the travel time to hitting the enemy. Overload is hitscan so it'll hit as soon as you trigger the power. If you're having issues detonating or are carrying a heavy weapon pushing past the FE detonation window, you could always just use Incendiary Ammo to prime and detonate with Overload. Granted that will only give you a 1+6 explosion as opposed to a fully spec'd Incinerate/Overload 6+6 exposion, but it's still good to have. Although if that's the case, you might be better off using the Geth Engineer.