Tier gear exists because that game, unlike FFXI, raised the level cap accross several expansions, which leads to higher levels of power and gear that should reflect that. Not all designs are perfect (see: any paladin tier set that is not T2, T9, and T10), but they generally have the right idea. Tier gear is not exactly a bad thing, either, specially considering that the vanilla design for tier gear used to favor certain roles. That's something we could certainly use, instead of "oh, RDM got yet another caster set... yaaaaay /sarcasm".
As far as companion pet battles, pankration says hi. I'll be amused if Blizzard gets it right, specially after seeing how quickly pankration died in this game.
Statistically, sure, people will have the same gear. They were intelligent enough to give players Transmogrification, though, so even when flying through stormwind city or perhaps running a raid you'll find people looking very different.Pretty much end result is everyone will have the same gear in the matter of days. And will be bored to tears crying for content.