The only thing LA has in common with d3 is the top down view.You can play all of the content including end game raids for free without spending a single penny.If you want to flex and get the maximum item level then sure you can spend real cash.
Remember this game has been out for 3 years, it is extremly polished and virtually bug free.It will run on an old pc very well, i have an 1080ti i7 4790k 16g ram and it plays on max 1440 buttery smooth on RU servers.
AAA games can only dream of the content that come free in LA Raids, 70 islands, housing on your own island, crafting, harvesting, mounts pets etc etc all account wide.IMO the polish and free content will make this a big hit.
Been playing on RU servers for months all free, can't wait for eu release!!
Edit....pvp is very balenced, every one has the same skill points and gear...its not a gank fest more skill based.