Karma had other strengths, there just wasn't any room for them in the old game. Spirit Bond was five seconds of +40% MS for the whole team on Mantra's 12-second cooldown, which is insane. It's just that lane responsibilities were less flexible back then, and her kit wasn't suitable for zero-income support.

She'd be fine today in weak-side top lane or two-item support, given two simple tweaks:

• Lower mana costs. Max-rank costs were 95/115/120, old mage design.
• Vision on W. Enemies could snap the tether just by stepping into brush.

She received both in her rework, so of course the new version is more viable. New max costs are 45/70/70 (and Q is flat), and Mantra gets its own scaling so her power curve is a lot better too. But we never got to see how these changes, plus the growth of the game and the meta, would have benefitted her old kit.