I don't think people grasp Slade's mental power, he is 10-15 times smarter than the average human, probably one of the smartest human strategists on earth.
He's the orginal "midnighter", he did the whole "fight in his head 100's of times before it happens" thing years before Midnighter.
He's so far above batman's mental capacity, that Batman even admits it and says it's nearly impossible to fight someone who is always 12 steps ahead of you. Outsmarting Batman is a big deal to me.
Then we have the issues of "Nightwing, Batman, Batgirl give him a hard time yada yada", Slade treats everyone like kids, he never really goes hardcore on them, always testing them like he's training them.
When he faught Batgirl, she said to herself that he always holds back on her, like he wants to see what shes made of. And she still couldn't take him.
He's been that way with everyone he fights.
Slade does rely on weapons more than h2h, but only because his job is to assassinate, he doesn't do it for fun. Why risk getting hurt when you have no personal emotions invested in the fight?
He is Wolvie's equal in skill, but his superior in speed(faster than WW), reflex's(enough to catch a lightspeeder), strength(2 tons), durability(immortality) and far far far far far far far far superior in intelligence and battle tactics.
Slade even has enhanced senses on par with Wolvies.
Wolverine's bones and super healing would be enough to make this an awesome fight IMO.
If written correctly, this would seriously be one of the best fights ever.