Generally an RPG is considered a game with a combat simulation system that is similar to those used by PnP RPGs from which the CRPG spawned. Simply having a growth mechanic is often considered insufficient.
But heck, even Vampire: The Masquerade: Bloodlines only had probably one more RPG element than Deus Ex.
It's a heavily debatable topic. There's very little formalization in video game genre discrimination. Even some of the older games of the CRPG heritage billed themselves as adventure games.
I personally prefer relatively strict assignments based on the most prominent aspects of the game and according to key examples. I think Deus Ex has far more in common with Half-Life than Baldur's Gate and would sooner recommend it to a Half-Life fan than a BG fan. Then throw in whatever qualifiers you think are relevant (action, adventure, with RPG elements, etc.).