And finally there is some small utility with Lightning Strike as a low mana ability which can also override HCI debuffs and can also potentially critically strike (Double Damage?).
Critical Strikes with LS deal 100% of full damage (ignoring all Resists) for that attack. It's a slightly more powerful AI (which deals 90% of full damage) basically. Problem is, even with 120 Bushido, Lightning Strike only has a 20% Critical Chance, so on average you'd have to deliver 5 Lightning Strikes to deliver 1 Critical. That's 50 Mana (excluding LMC) worth, when 1 AI is 30 Mana (25 with 120 Archery/80+ Bushido, excluding LMC). Even a chained AI that has it's Mana Cost doubled, ends up being 50. Non-Critical Lightning Strikes deal no more damage than regular attacks, and if you're already capped at 45% HCI, then the +50% HCI from LS is useless (asides from when HCI is debuffed). 80% of the time, you're spending Mana for no benefit, even worse if you have less than 120 Bushido (only 13% Critical Chance at GM Bushido). They really gutted the usefulness of Lightning Strike when they doubled it's base Mana Cost from 5 to 10. Especially nowadays when it's easy enough to get enough HML on the bow and deliver enough damage that you can endlessly chain AIs all day. For melee, who have even more Mana Leech capability, Lightning Strike is completely pointless.
If you run low on Mana and can't AI, then you're basically better off just saving the Mana and auto attacking once or twice then continuing AIs, than using Mana on a Lightning Strike.