as it stands i feel a shadow demon str per agi will be an auto attack god and if heals from other players dont take from your life then i think in group fights it will be easily the best race in the game for melee and constitution is somewhat a dumpstat, if other players heals do take from your life then i think it will be a very effective assasin in group fights but will quickly wither if too much heat is put on him and his life bar depletes quickly under pressure and you will feel the lack of constitution (this is my preferred reality )
in that case then a beastman bear with high con str and semi high int would make someone who can hang around in the thick of it healsponging for longer sacrificing attack speed, evasion, accuracy and crit chance/damage but giving me wider variety of abilities to use from strength and constitution (and magic if i choose to use less armor but i have trash evasion) in my build and maybe even a self heal idk ^.^
for me it hinges on the final product of the endurance and life system i think it will be amazing if heals to endurance mean a subtraction from life always (barring some special skills maybe) and you could have heals to life subtract from the healers life getting more efficient as you gain knowledge meaning people could maybe play a constitution healer and feed life to glass cannons to keep them on the frontline for another layer of interesting to fights