Dear Blizzard,
Thanks a lot for giving me access to Alpha ! I tested all i could.
I found some issues/bug/differences from original. Some of those changes can have an impact on PvP and also PvM.
At first, i made videos with explanations on everything (exept the first) to make it clear.
My Diablo 2 Channel : https://www.youtube.com/user/DHAForHe/videos
1. Extended range screen
I have to repost it here because it is a really important one :
Extended range on wide minotor can destroy the pvp and break the actual balance between players.
More than that, it makes PvM pointless with a view from the moon.
I’m not here to give solutions just to report problems (even tho a solution is to put a limit and make a zoomed view on wide screen).
2. Mouse and Centered map bug
While opening tabs (c/t, quests etc.) mouse is moving.
Also the centered map is no longer centered.
Video that show it : https://www.youtube.com/watch?v=1Gt3mg72f-E**
3. Textures bugs on some areas at Fast Speed (105 fcr).
Some “textures” bugs on some area. Maybe it’s my spec but not 100% sure.
Video here : https://www.youtube.com/watch?v=U4vyFUm6PmM
*Spec for info : *
*Proc: Intel Core i7-7700K 4,20 GHz U3E1 *
Memory 32 Go
Graphic: AMD Radeon RX 5700 XT
Screen: ACER XF240H 144hz (gsync)
4. Noticed hard FPS drop on monsters pack
5. "ALT or “Show Items” hotkey is bugged
It doesn’t work as before.
PvM aspect :
Holding Alt should prevent you from interacting with anything besides items on the ground. Alt wasn’t working properly in the Alpha.
*For example, you could talk to NPCs or enter TPs while holding Alt.
PvP aspect :
In PvP, it was a must on Whirlwind Barbarian to avoid Whirlwind bugs, whirlwind interruption etc.
Video that shows and explains all : https://www.youtube.com/watch?v=6QseUa3sYJ8
Also a video that shows what is a “Whilrwind bug” on Classic D2 on a barb that did not use “ALT” when he whirls : https://www.youtube.com/watch?v=ygLjLsgTcZA
5. “Chainlocks”, “Teleport Chains” and “Double teleport Blind spot”
What the hell are you talking about DHA? 
Those are pvp features but i tested if the mecanics works on monsters.
Chainlocking : It’s when you make namelocks in row and then you follow your opponent.
You namelock him with a skill then put mousse in middle of screen on his name and you teleport and renamelock him, then tele and relock him etc.
It seems to work on D2R as original D2.
Teleport chainlocking: Kinda the same mecanics but you don’t “renamelock” you just hold teleport on his name and then you will follow him.
The purpose of the mecanics seems to work, however it’s not the same. The animation looks like your character is “stand still” on top. (look video after)
“Double teleport blind spot” : On Classic D2, when you make a double tele chains on a standing still opponent, you will appears to be at his right side not on top (this side is called the blind spot) (look video after).
It does not work in D2R since you stay on top.
Video that show that chainlocking is working and that Teleport chainlocking is “different” : https://www.youtube.com/watch?v=hrm61E7OzFg
Video that show that Teleport Chainlocking might still work but anyway the “Double Teleport Blindspot” doesn’t work anymore : https://www.youtube.com/watch?v=h2BgHKZjYHo
6. c/t Casting works by holding skill not clicking as before
What is c/t casting :
"The name of the C/T Trick comes from the default binds that are used for this technique.
C — Character Screen
T— Skill Tree
The thing with this trick is that when you open certain game screens (Character screen and Skill Tree) we can increase the radius (more like the rectangle) of skills like Teleport and Lightning Sentry. "
7. Whirlwind has delays
Whirlwind changed in D2R, it now has delays, it stops and restart.
You can’t “non stop whirlwind” as before. It’s clearly not as smooth as before.
A problem in both PvM and PvP.
Video here, D2R, D2R Legacy and Classic D2 test : https://www.youtube.com/watch?v=S5xRiQzwpSk
Oh yeah, some people made lvl 99 chars in Hell 
and shared them. It’s Single Players but i guess you should take a look 
At least it helped to test the game.
I know for some those bugs are not a big deal, but for some others it is.
Also it’s not a big deal fixing some of those i guess.
I hope i helped. The game is a masterpiece.
Regards,
DHA