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It was not in the regional dex, but Deerling was catchable through the DexNav in ORAS (I think it was one specific form only, but don't remember).
In X/Y you could get Sawsbuck through Friend Safari.... which I never used tbh.
I don't recall Emolga giving me any troubles in gen 5.
I do remember a sky battle in X/Y where it killed my birb, because I had nothing to deal with it xD