my shpecker, if you're not trolling, here's what you're missing: this game is trying to be a balanced and competitively-oriented game. Not a "pick Jedi/Sith if you want to win, or pick any other class if you want to die" fantasy roleplay game. Gunners have to have a chance, or there's no reason to use them.
another way to look at it is: those Jedi and Sith who you see cutting through enemies in the movies are much better at playing Jedi/Sith than you are. Get gud son. Besides, from what I've seen, at most skill levels (except very high and very very low), Sabers do dominate lone gunners.
another note: i don't think one ever really sees Jedi charging head on into gunners and just cutting through them in the movies? From what I can recall of scenes from the movies and the tv show, neither of which i've really watched, saberists always seem like they have slow, measured advances, with a heavy reliance on Deflect and on support from allies. I'm sure there's some exceptions (Vader in Rogue One), but at the same time, i don't think there's any seen that shows, for instance, a lone Jedi charging at a battalion of soldiers and surviving. That "gunners have strength in numbers" concept is important, and canon.
also, cutting down a bunch of battle droids is a bad example anyway since battle droids just kind of meander idiotically forward waiting to be slashed in the side. Yes, there's a Battle Droid soldier model in-game, but the soldier class in general represents a person with a regular brain but no super powers or plot armor. Maybe a skilled person, but still a person who will probably die at a moment's notice without anyone caring.
another note: in Order 66, and in the Clone Wars arc where Order 66 activates early in one trooper, then it's shown pretty clearly that a few shots to the back of a jedi will kill them. They are not physically tough, but they can defend their front really well, which is entirely true in MB2. I really don't know why you think Jedi/Sith ought to have a lot of HP. They already are incredibly hard to kill, and if you don't feel hard to kill then you need to get gud son.
another note: if you want to Vader-style dominate groups of gunners with the Sheer Power of the Dark Side, learn how to combo lightning into saber. And actually, all four of the faction-specific seem to be oriented around destroying gunners who aren't supported by ally Jedi/Sith. so use em if that's what you want.
and if you still die, it's your fault, you're not using the force, you're not playing as well as Anakin would play