outside of cosmetic bullshit for d4, d3, immortal, and wow the only reason to get the standard edition is if you want to pay the least amount of money and get early access to beta this month.
get deluxe if you want "up to" 4 days early access to the game and a battle pass. get ultimate if you want the 20 tier battle pass boost.
i'm going with the Ultimate Edition which is £90 here. Standard is £60. I don't care about £30 and even if i went with standard i'd still probably buy the battlepass. so really for ~£20 i'm getting early access to beta/launch, all the stupid cosmetic shit, and the 20 tier boost.
as for D2, i haven't played it except during the beta. i thought it was good but what do i know? seems to be well received from what i can tell. i bought it but haven't got around to playing it because i'm waiting for IV.