I could see Assassin's Shroud being a good item on her. It'd help with both her disable and her ult.
Edit: Also, damage reduction being spread over several attacks has no effect on overall damage. (.75 x 165) + (.75 x 165) + (.75 x 165) + (.75 x 165) + (.75 x 165) + (.75 x 165) + (.75 x 165) + (.75 x 165) + (.75 x 165) is still equal to .75 x 1485. Which incidentally is more than twice the damage of Wretched Hag's boosted ult.
Edit 2: And what about jiggle physics?
Anyway, I tried Engi and had a ton of fun with him - great animation, lots of great skill combos you can pull off with this dude, and of course the obvious TF2 inspiration helps too (Scout sappin' mah sentreh!). Seriously though, a cheap, fast, non-channeling, low-cooldown ward that scales with items and gets their procs? Oh baby. Seems like an ideal mid (sentry camp rune spawn = lolz), although you can tell he was designed to be a jungler with HotBL right in his recommended items. Definitely gonna be playing more of this guy.