What's The Benefit Of GM2 and GM3?

How big is the jump from Gm1 to Gm2?

As GM1 gets easier with gear increases. I know that Legendary and MW drops get better drop rates going to GM2 or GM3. So tempted to try a GM2.

Oh, it's big. Bigger than Hard to GM1. More like Normal to GM1.

In GM2 enemies hit 3x harder if not more and have probably 3x (but could be more) health compared to GM1. I find the difficulty worthless waste of time since the drop rates are not 3x more and it's debatable if there is even a drop rate difference. My best GM2 SH run gave me a Legendary and 2 MW drops outside the boss MW. My best GM1 SH run gave me the same rewards.

And in GM2 gear rating means nothing. You can be in full Legendaries and useless. Don't even bother going in SH without at LEAST 150% extra damage on your main weapon/ability. I mean you can, but enjoy taking out the weakest mob in more than 30 seconds. You need loads and loads of extra damage, shields and health. Synergies help and it will suck if someone in your team screws the setup you have (had a Colossus in 320 gear in GM2 going crazy with the fire and preventing me to build my combos and Ultimate. He did like zero damage anyway, but wouldn't stop even when asked. He would have been more useful by afking.). Oh and your badass Ultimate? Enjoy watching how it takes less than half the health of an Elite mob.

Well, to be fair. They WERE going to have GM2 and 3 disabled at launch remember? But everyone cried about not being able to do it. I think it's obvious now that Bioware knew GM2 and 3 were not "ready" and didn't want to release them in the state they are in. Honestly for now, it's truly best just to stick to GM1 imo.

I had this exact same thought.  It's only because of all the whining that they were turned on at launch.  And of course, it backfired somewhat.

After 1.5 hours

Did get 3 Legendaries at GM2 in last 5 missions, 2 of which were in the 5th match just finished a moment ago;

Luck at 98%.

The challenge.