As someone who was obsessed with Diablo II, I still found Diablo III to be pretty darn fun and it's gotten MUCH better with time (it was quite flawed at launch to the point that I initially lost interest). I'd absolutely play that on the Switch... I've really enjoyed playing games I loved on the Switch in handheld mode, so even though I already have it on PC and PS4 I think I'd get it again lol
does it involve a lot of grinding?
switch has been effective on games that involves a lot of grinding :P
Actually, if I have one complaint it's that it's much too easy now. On release I played the hell out of it to the point that I was at the leading edge of progress among barbarians, and it increasingly became far too difficult. This wasn't particularly a surprise, as melee has always been at a disadvantage in Diablo games as you progress through greater difficulties and encounter enemies with extremely painful AOE buffs upon hitting them... when standing at a distance these can be dodged, but up close you just need to load up on resistance. My main criticism was that the gear and/or class resistance did not remotely keep pace with what was necessary at the time to play the Barbarian class effectively and not be a hindrance that largely has to stand back and watch for long stretches.
I came back to Diablo 3 when the new version with that expansion released on the PS4, though, and found that it was waaaaaaaaaaay too easy. I noticed when I was deep into the Paragon levels and farming those portal things you could make that I still hadn't even gained the in-game achievement for "nearly" dying but surviving to recover. This meant that in all that time maxing out my level and farming I not only had never died but never even got down to under 20% health. That's just absurd as I am definitely no Diablo savant or anything lol
The truth about Diablo, though, is that lots of the appeal actually IS grinding to an extent... what kept people coming back was the combination of challenge with the gambling nature of hoping for something awesome to drop. The only people who will remain interested long-term, then, tend to be those who enjoy that eternal pursuit for better gear and growing increasingly "wealthy" via trades and such. I don't honestly know if this game has some equivalent to SoJ's and WF's from Diablo II which came to essentially serve as a currency, but if they do I might get hooked again lol