Naw, but with a coordinated team he can steal kills. And early on, before he gets Eblade, he can morph strength to bump up his survivability and then have a pretty nice stun to help out everyone else. 3-second instastun on a 10-second cooldown? There are worse abilities out there... Especially since his waveform damage isn't affected by his focusing strength, so it's still a decent early nuke on its own.
And it's not like Void or AM and their kin are particularly effective early on either.
Naga to me just seems like a Cancer Lancer Lite. She's got some sweet abilities and slightly greater individual versatility because of it, but just can't match the Lancer's swarm and pushing ability. More of a team player than a player team. Still though, against illusion-vulnerable targets? Gawddamn. Especially with that 5-second root and her armor debuff... And her ult can make for a hilarious entrance because she can just sidle up to her preferred target and Manta+Mirror to get all 6 of her right next to them and just start the slaughter.
I've started to develop unhealthy infatuations with specific items... Before I was madly in love with Ring of Basilius, but now I'm building Soul Ring on loads of peeps. Centaur, Juggernaut, Treant... All great candidates. Nowadays it's actually fairly rare I build anything off the default Valve recommended items, so I have to customize my own builds just to have an easy-access menu, haha.
And next time I roll Leoric, I'm building Blade Mail. Just for kicks. Also Soul Ring, because that synergizes just too well with him.
EDIT: Oh, haha, Dagon... I just played a game recently where someone played Dagon Void. Rushed an early Dagon, then Blink Dagger and... Something else, I forget. That's even more ridiculous than my Manta Void build. Hilarious fun though.