Just incase it helps, info on how Energy Siphon is suppose to work from patch notes
Updated Energy Siphon:
The self-buff portion now has the same duration as the debuff on the target.
Flow Capacitors no longer modifies the duration of this power, it now modifies the magnitude.
Duration has been slightly increased, due to Flow Capacitors no longer increasing it.
Flow Capacitor skill has a larger impact on Drain amounts than it does on Buff amounts
This is in order to balance against opponent resists.
Power Insulators reduce the magnitude of the debuff if you are targeted by this power, but have no effect on the buff the user will receive.
Debuff can be cured using Science Team or Hazard Emitters.
This has no effect on the buff portion of the power.