I sometimes use AI3 to test decks for PvP use... I guess I'm just frustrated that the variety of strategies used in PvP can't be pre-tested with the AI used for those. I wonder if it's a server space issue, but I see a bunch of themed strategies that could be added to the AI3 decks.
I wouldn't mind a few shards being added to the roster, considering most of them are less formidable after this recent update. A few of the less OP ones would be cool to win from an AI on a spin.
Most shards are still useful, except for the ones that were already UP before the update. If only the UP ones were added, that wouldn't make sense, as they are rarely used and you still wouldn't be able to test your deck against all PVP varieties as you claim. Not only that, but it'd also be rather unconventional and weak, and easily steamrolled as other decks in that rooster are.
Not only that, but that would break the purpose of Arena, if only just a little.