Also should we not expect a Beginning Game - Middle Game - End Game RPS in our metagame?
And where is dimensional shield in this RPS?
Dimensional shield crushes the early game, drags the middle-game into the end-game, and prolongs the end-game to silly levels when used at the end-game.
(Assuming when it's not answered.)
No matter when you use it, dimensional shield is always a good choice.
This isn't entirely accurate, as it always takes you a few turns to get the quanta to play Dim in the unupped scene. Additionally, and this is rather important, you never want Dim to be the first thing you play. First you want offense out to put your opponent on the clock.
While Discord+(BH/EQ/mass-PC like BE) aimed at the opponent's quanta sources isn't a direct counter to Dims, it remains an effective one. Since the quanta denial combo also takes a bit of time to get running, its weakness is also the early game and sometimes still loses to a Dim deck because it managed to get early offense and a Dim out. A mono Dim deck does tend to pack a lot of quanta and therefore has a small unintended edge against denial decks. Duo Dim decks tend to be easy prey, however.
In all other games, if you only have a bit of damage that'll go through Dims, the early game is still what you have to bank on. For instance, a Giant Frog+Epi rush with 6 Deadly Poisons off mark can't win with just the Poisons, but it has to put in as much damage early on as it can. The same goes for an upped Monogravy rush; the Electrocutor will make sure your Elite Chargers only deal 7 damage unless you play several in a turn, and so you have to draw and play your Guards early to do damage before the Dims are up.
Early game is definitely a weakness of Dims that people often try to exploit. It can be hard to successfully do so, but perhaps that gives us a tool to work with that allows for a nerf that isn't all black or white and makes more soft counters better. By increasing the cost of Dims (e.g. to 8
), you can extend the early game by a turn in most games and make the upkeep noticeably harder mid-game which may very well be all that decks like UG+Fog+Dragon needs.
Edit: A noticeably increased cost of your core card also makes it much harder for a Dim deck to pack all the support cards it wanted. Right now, Dim decks can easily pack both Lobos and Lightnings and will still afford Psiontal. While a 14-16 quanta Psiontal is faster, it can easily be run with 12 quanta. With a higher cost on Dims, that'd be much, much harder and that early rush deck with soft counters to Dims won't run into Lightnings, or the MA might just not be able to afford Lobo early on to completely neuter Chargers/FFQ's/Pharaohs/Blue Nymphs/etc. It'll most likely still afford Lobo mid-game, but that gives the other deck quite a lot of leeway.
2 cost may look like little, but it shifts the entire pace of the match forward.