You are right about Charge. I started playing Insanity with my Vanguard, and gave up pretty early. You can't really use Charge at all unless there are 1 or 2 enimies left or you will die very quickly. At least that's what I found.
What I've found is that Charge is basically lame without the claymore shotgun (and its 1-shot has become a severe limitation). Without using Charge (say you chose a rifle as the special weapon), Vanguard is a fairly crippled class with weak armor/barrier and moderate crowd control skills (assuming the enemies have no armor/barrier).
I'll see how it goes when I start accruing the various upgrades...but right now I'm pretty sure attempting Insanity would just be a frustrating waste of time.
Vanguard is damn fun on Normal though. My original character was an Adept anyway. I'm thinking bastion + reave + pull or singularity + sniper would be a pretty lethal class.
edit: Now looking the the weapon stats on wikia, maybe the Eviscerator is the better shotgun due to clip and range. Wish I could re-specialize my weapon (eviscerator hadn't yet been released).
edit2: After playing with the Eviscerator last night...the Claymore is definitely much more powerful. I just gotta work the enemies down with reave, overload, warp, incinerate, etc...then I can charge in and blow 'em away. It'll get better as I get more upgrades, but damn some parts are frustrating as fuck.