With Dragons many people would probably seek them out for knowladge but in alot if western media Dragons are seen as, mostly, inteligent beasts at best &, at worst, talking monsters by the common peasant. The fact they have been hunted the way they have makes me beleive that they are not considered civilised by the other races (I feel the title "civilised race" is used by the Humans, Elves, Dwarves, Halflings & such meaning it's less what WE think & more how these graces perceive others).
Merfolk could just as easily be an aquatic off-shoot of man or they could be a form of evolutionary neich that just evolved like aquatic simians. But again if their only interactions with "civilised races" are through fishermen & sailors they may not be considered so.
Ents protect the forest & live, essentially, nomadic lifestyles. Their nature would put them at odds with any form of industry, the thriving heart of civilisation, based entirely on conflict with loggers & lumberjacks... so again I do not think they would be considered civilised but just another form of inteligent monster or entity.