Warcraft Dragons are master shapeshifters. even beyond what Druids are. like apparently one became a tree. they take on mortal race appearance for convenience and to infiltrate their ranks. as such, i dont see why the dragon experiments wouldn’t be able to change what mortal race they appear as at a later point.
as for combat, well, currently much of the Evoker makes sense combat wise. its the combat utility and tools granted in that form. and generally thats fine imo.
however, there are other creative ways to get around it. like how DH wings may only come out when needed. so someone wanting to fight while only looking like their human form could work.
personally i would want to use the amazing dragon form.
Dragons seem more physical combat oriented with some ranged abilities. given that they are a combination of all 5 aspects them being engineered to be more caster oriented seems fine.
i could see a 3rd spec being made that incorporated the abilities of other classes as their spec specific tree while keeping their core dragon portion of the tree.
such a spec would be amazing option wise. it would prob also be very complicated.
but BUT that could give them such combat visuals as using a sword and or shield. a spear or ranged weapon.
a dracthyr warrior with evoker base abilities like a breath attack, wing buffet, and short range flight.
maybe a Dracthyr priest combining some holy spells in with their time magic.
A truly versatile hybrid. that is at least what i think they were intended to be when they were created.
can a failed creation reach a point to where they succeed in reaching or growing to attain those expectations?
as for the dragon visual. it could use more Options in terms of build types. i like how they look now but i have see other edits that people have done that also look quite good.
in terms of armor, Dragons dont need armor however, they often have armor as accents or flare. so having both visual options would be good. getting the armor system to work on the dragons would give a large array of customization to them. but at the same time, it would feel odd if they had to always use that armor system when most dragons dont.
maybe if the barber shop is where the hide/ show toggle is for the dragon specific items also had a toggle for the transmog show/hide.
or maybe, even better would be for the transmog window to have a save xmog for human form separate for save xmog for dragon form. and there Dracthyr compatible xmog could be selected. extra hide sections specific to the Dracthyr pants because dragons dont need pants in the same way other races do. 
Now for worgen comparison. the Worgen has Running wild.
Druids have Flight form.
out in normal zones, Dracthyr SHOULD be allowed to activate a persistent flying ability sperate from the normal glide ability. maybe call it wild flying. or what ever.
i still think Dragons should have a tank spec. that visual makes sense imo. and maybe…
What if Druid Guardian got a Dragon appearance, simply for the sake of making that visual possible without needing to create a Dragon tank spec.
or maybe, Make a Dragon Black Flight focused Earth power tank. and have that added or unlocked much later into the game. maybe 10.1 or 10.2 or even 11.0
wouldn’t be the first time a class got a new spec
I would imagine a Dragon would draw a lot of aggro simply by existing. never mind all the Dungeon/ Raid bosses that are Dragons and often melee focused.
i also agree, we dont need more melee specs but a Tank isn’t taking a melee spot. it goes in a tank slot and there are not that many tanks when compared to dps or heals.
without it getting the tank options it makes tanks the lease numerous option. think it was something like 6 tanks 13 melee 12 range and 7 heals… if memory is working correctly 
also, also. i think Dragons should have a ground/ all four running dash attack with a sort of upper cut finish because i think that would look cool. 
