With the release of the Treecko line, all 3 Hoenn starter lines are now available in Pokemon TCG Pocket. Unfortunately, they don't have an equal presence.

The meta of the early season has Mega Blaziken as the top dog. One of its few counters is Hydreigon, which is in turn countered by Mega Sceptile. (You can guess Mega Sceptile's counter.)

There is a rock-paper-scissors dynamic here and Mega Swampert is not in it.

Edit: early-season meta shifts fast. Mega Blaziken may be fraudulent after all.