As a rare at 15 mana, I’ve yet to find it actually be useful during a battle, and a rarely see it played in the decks of others during quick battle. Do any of you actually have a use/strategy to play Mage-Ring Responder?
It is not used because it is unreliable.
The only pwalkers that I think have a marginal better chance to use it properly are nissa an Chandra once leveled 1st skill to max.
So at start of turn you see if there is the 5 match needed… If there is not use the first skill to try and gray cascades that could lead to the chance of making a 5 match.
That is if you reeeally want to try it. I would suggest just to not care 
I used to use it in Gideon. His first ability to makes it a sturdy defender.
I only use it in story mode with Gideon where the objective asks me to hold for 20+ rounds or kill certain number of opponent creatures.