Problem:
Synergies are hard to use because the pop up is impossibly brief.
Some synergy pop ups seem to move around with the caster and not the area of enemies effected(Impale?).
Some synergy pop ups turn on and off if you stand on the edge of an ability or have a microscopic activation area.
Stacked synergies require random use of synergies to get the right one.
Sometimes it seems you have to press X more than once to activate a synergy because they are less responsive than their pop up indicates.

Suggestions:
Synergies need to stop blinking in and out at light speed and be solidly usable for the entire duration. Make them either on or off and have an area and duration equal to that of the ability used.
Synergies need to be usable immediately and responsive when an ability like a spear lands, not after .5 or 1s and not after the second press of X when the pop up is displayed.
Allow second, third or fourth synergy keys to activate other synergies like the Templar spear instead of X for Conduit when synergies are stacked.


Conclusion:
Synergy activation pop ups should be differentiated for use when stacked, solid and easily activated instead of blinking or slow and not microscopic or tenuous in area.