4v4 doesn't mean all games will be sweaty. You can still do everything you want. Halo 3 social was far from sweaty and they managed 4v4
If you want to win or just not have a bad time it does. As soon as one person goes AFK or leaves, or is just quite frankly, not very good, then you're gonna have a bad time due to the team-shoot to kill mechanics.
You're no longer going to pull off something awesome in a 1v2 or 1v3 situation due to ability nerfs and/or changes to the damage model.
Besides all of that, the simple fact that 4v4 exists just makes no sense as the numbers don't work into anything for grouping up in other content.
Strikes? - Groups of 3.
Raids? - Groups of 6.
You'd need a group of 12 just to make it so that nobody is left out, which is fine for most of DGAF as there's loads of us but it's plain bad game design that PvE has been gimped to allow for more "balanced" (Read bland and boring) PvP.
Just like pretty much every change they've made in regards to D2, they've taken away "choice", in the favour of "balance".
Multiple PvP modes of varying map sizes and team sizes? - Gone.
Multiple perk choices for each subclass? - Gone.
Multiple weapon types for each of the 3 groups? - Gone, secondaries merge with heavy. Pick two primary instead.
There is literally not one thing I can think of that has been changed, which gives the player more variety and choice, which in some way, is not detrimental to another aspect. Not a single one.