Serious trained Karate could give you cardio, bone conditioning, reflex, resilience, good kicks, elbows, and knees, dodge.
It only lacks punching in the face, for the karate filosofy is to trade less as possibly, so we are not used to keep trading punches with gloves, so if you intend to learn karate as a stand up mma base, you better complement it with boxing or kick boxing.
As for self defense, karate is very effective.
But keep in mind that most karate gyms now a days are giving very poor-sport oriented training, as my sensei says "if you are not getting tired, and feeling pain, the training is not working!!".
For further info about karate mma fighters I recommend you yo see Lyoto Machida (from Shotokan), and Andrews Nakahara (from kyokushin).
And in k-1 Glaube Feitosa, Francisco Filho, Everton Teixeira, Semmy Schilt, Fabiano Silva.