Overall, the issue with Grom is that there is too much overlap with TWO characters now - His WC3 kit (Really the only definitive one) is pretty much the entirety of Samuro's kit, and his profile overlaps quite a bit with Garrosh.
Granted, Garrosh's own kit came as a complete surprise (As has many other characters), and we have several other heroes with profile overlap (Rehgar and Thrall), so... who knows?
Anduin and Varian have both significant kit divergences (Anduin = Priest(Pre-BFA)/Paladin(Post-BFA), Varian = Warrior) and profile divergences (Anduin being young, naive, wanting peace, Varian being old, pragmatic, and no-fuckery). Do note that in WoD, Garrosh was actually OLDER then Grom, so rather then the old king/young prince-king Varian and Anduin gots going on, Garrosh and Grom would be middle-age orc warchief, and... middle-age orc warchief.
Really, Blizz made a mistake when they released Garrosh before Grom. Garrosh had ALL kinds of way his kit could have gone. Grom... Well, eh, Blizz has to be creative.
Mechagnomes are again, just another reskin of something that we got. Vulpera on the other hand is completely new. It uses the goblin skeleton but it looks 100% new. The better counter for that would be those snake people for alliance, the sethrak.
I was really hyped for this feature before release, but it seems to be getting a bit out of control. If they keep allied races coming in the current pace in a few expansions time we will have 40+ playable race in total and 20/faction! That's crazy and while they all had some nice introduction quest to them so far, they certainly don't have such an epic entry to the world as say pandas had (I'm not a fan of pandaren, but they had their own dedicated starting zone, lore, art, etc. to make them feel relevant). I don't know how will they try to develop the story of the races in the future, but they surely don't make it easy with such a multi-cultural setting.
Tyrande is an interesting case because she also has some tidy bits of Hunter in her kit (Hunter's Mark, Trueshot Aura).
I can definitely see Anduin borrowing some Spells, or modified ones, from the Priest's Holy tree, but also having some uniqueness. In WoW, when fought at Stormwind by the Horde, he has Greater Heal, Penance, Power Word: Aegis and Psychic Scream. Out of these spells, I imagine him having at least Penance and Power Word: Aegis, in one form or another.