I'm not the best with numbers but these will give you an idea:
Overload primes for a duration of ~5 secs. So, if you (or your teammate) casts another power capable of detonating a tech burst (like incinerate, energy drain, most grenade powers, throw, etc.) in that duration, a tech burst will result. Similar mechanics for incinerate (duration is ~8 s if you choose 5a evolution).
Casting overload, then casting drone is not good for tech bursts because the drone detonates upon exploding, which would require enemies to actively target it. My usual attack cycle involves drone > shoot > overload/incinerate > shoot > if drone explodes, power combo happens, else I detonate with incinerate/overload. And so on. (I only cast the drone if I see multiple enemies close by or if it's a heavy armored unit).
P.S. My numbers could be off but every power has a duration (most of them are listed in the power tress) but some are hidden mechanics (like overload, energy drain, etc)
I beg to differ, Incinerate has a priming window of 3 seconds but does DoT for 8 seconds with the right evolution. I am not sure on the Overload issue, though.
@czeuch People basically do 2 builds for the HE - with drone and without drone. If it's without a drone, then the HE becomes a powerful one-two punching machine with in-built crowd control. And you either take non-priming ammo on a light weapon, or a priming ammo (i.e. Incendiary or Disruptor) on a heavy (-hitting) weapon.
If you take the drone build, people usually put all 6 points or just 3 (mostly to use it for distraction purposes). I personally roll with a 56645 build, but what can I say, I'm special that way.
In this scenario you typically do what TNS said - spawn a drone in a group of enemies for distraction and some stagger and then continue spamming your powers. Sooner or later someone will kill the little disco ball of wrath and will thus detonate a power combo, cause both your other powers are primers.
2 things - First, power combos of the same type have different levels of damage. Basically the level of damage is the sum of the levels of the two powers involved, i.e. from 2 to 12. If it is a tech burst/fire explosion caused by ammo, then it counts as 1 + detonating power level (i.e. from 1 to 7). Second, if you evolve the drone past the first 3 levels, always pick the Detonate, Shock and Chain Lightning options. The others are shite, especially on Gold and Plat.
p.s. If you troll regularly geth, phantoms or Atlases with the drone be sure to yell "You are stupid, tralala!" for extra cool points. 