Here is the Deal, Warhammer starts in 80s or w/e. Blizzard tries to buy WH from Gamesworkshop, gamesworkshop says no so instead blizzard makes warCRAFT and makes it very similar to warhammer. blizzard makes wow based of warcraft based of warhammer. mythic makes WAR based of warhammer.
That is why the artwork is so similar the look. As for the UI that is all similar becuase its a nobrainer for mythic to make a UI based off of something 8 mil ppl already play (wow), except they have improved on it.
Its alot faster paced, no grinding, it essentially removes everything from wow that is boring or tedious, and aims to improve on the rest.
Another great thing is they are no a war path to ban all gold sellers/spammers, ZERO tolerance, its great to see a game look after the integrity of the idea.

Dont take my word for WAR being better look at all the other reviews, and alot of the negative things ive read a simple things that future patches will no doubt clear up, just as WOW has been years in development, so will this and it wil only get better.