@ridtom: I'd wager Batgirl (CC) has speed feats equal to or better than Hei and she was overwhelmed by Deathstroke. As for the Nth metal armor conducting electricity that was not my point...
It provides magical enchantment that increases Deathstroke's physical abilities and provides supernatural protection from harm, I don't see why electricity would be immune to that effect. Not saying it definitely stops him from being electrocuted but it is worth taking into account. You also completely ignored my point about Deathstroke's superhuman physiology which likely provides further resistance to electric attacks.
As far as Hei being able to do "much, much more" what exactly are you talking about that could be useful here? I'm assuming he does not have any power-ups like the meteor fragment, which OP would have specified. That would make this fight completely unbalanced anyway. Aside from times that he was amped Hei sticks to regular electric shocks 99% of the time.
Also, Batman can land hits on Slade because he is far better than Hei at hand to hand combat, being master of 127 styles of martial arts etc.
How does Batgirl have better feats than dodging/blocking point blank bullets and sonic boom inducing kicks?
His physiology would give him an some resistance to electricity, but Hei can pump out quite a lot of it, enough to kill him at least.
So it's magical in nature? Has it been shown to resist electrical attacks?
I'd argue that Batman and Hei are roughly equal if only because while Batman has the skills, Hei has the experience of fighting super-powered individuals without powers in a major war.