I agree on many points but I want to be more gray about it.
Yes the timing of the melee combat is tight but it is challenging in a way.

The issue I have however is that the combat is reduced to button mashing at some point. There is no rhythm or pattern to combat. Ether mash attack to not be grapple or spam dodge to roll away. I'm pretty sure that something could be done, like add a rhythm to it. The batman arkam games did a good job of rewarding player who do not mash and use the rhythm to land punch with crits. I'm not saying that this game needs critical melee hits. It's already superfast. Maybe something else like special refund or lifesteal?
 By the way, the dodge is definitely the least useful move because the recovery after it is way too slow.

Another thing is that the sound cues are really useful in a melee combat situation. You shouldn't play this game with music on. The grapple sound cue (and visual effect) let you react just fast enough to roll around a corner or to turn and punch. And on the opposite side, if you want to grapple, you have to be smart about it. Leaning along corners, jumping out of nowhere. The sound cue of the antagonist respawn is also critical for your survival.

About the 3vs1 situation you described, sorry to say but if you got cornered that way, it's on you. You shouldn't be able to slip away. This game punishes runin' gunbazin' and that's neat. I watched people simply ignore the stealth mechanic completely and that's no bueno.  This game is focused on awareness of your surrounding, attack planning and fast execution. But (and I'm leading to my last point) all of this is hard to feel/understand in the first few hours.

The tutorial is way too light. The gameplay and the gamesense are hard to swallow and the tutorial give nothing to help you with.  The first mission can be an unpleasant experience if you find yourself cued with a good antagonist twice or thrice. I remember that in my first games, I was doing random things, like all rookies do. But the first mission is unforgiving with that (especially at the last part) and the addition of an antagonist in your first/second game ever can turn it into the last game ever. At least for the first mission, you should be protected against antagonists and a second tutorial should be unlocked after, teaching some tips and tricks to play/counter antagonists. And to end it, little conclusion, taterthot style:

tl;dr melee needs tinkering, tutorial needs a complete rework.