Hey Mael. I guess the points about a less strategic fantasy have already been made (and are valid) but to answer your other questions: Orcs and Gobbos are always fun and silly when being played. The army can of course win but to do so (as well as tomb kings) there is a synergie of units required, neither army can field the I WIN death star such as how other ones do, this will probably be a trend with 8th ed army books ie that they are a bit softer and require a decent army selection to work. Warriors of chaos are very very good now. The game revolves around infantry and big units of them so warriors can do this with some of the best sledgehammer deathstars out there. Not to mention they have some nasty magic items and can get 3+ ward saves on chosen and on their characters. But the army has one weakness and as a dark elf player this is what I exploit. Unlike any other fantasy army, warriors always play the exact same, always. You can count on them having to advance towards you and engage you with their death star, you know they have nasty magic and nasty heroes, but this can be dealt with. So the trick with beating them is that you can know how they will play and the trick with playing them, is to figure out how to play them in a new way (which so far I have never seen). Lastly, Empire are much more competitive now. Take a huge unit of hobo's and the pope-mobile and then max out on a gunline and there is little that will win against that (except lizardmen, skaven and warriors) everything else gets completely pasted. Otherwise the army can be played traditionnaly with big blocks of state troops but since cavalry are realy nerfed in this edition, the cannons compensate for a lack of hard hiting units.
What you have to remember about 8th ed is that it is a beer and preztles game and few people will say otherwise. It is no longer meant for tournements (which is why i do not like it) but it is fun to play with your friends. That being said some builds are absolutely rediculous so don't listen to people who say the game is balanced, it is not. There are a couple builds will almost always win, like nothing ever seen in 7th ed or in 40k. So if you want competitive lists to play against there are plenty of them. Or take my approach pick your favorite army (dark elves ftw) and don't give a S about rules that cannot be changed and have fun since you love the army and enjoy playing games with your friends.