It's been brought up before, but I'm going to bring it up again. Silver Sheild and below should use the 1/2/3/4, L/E/R/C scaling method that Challenge modes and Friendly fights use.
Silver and below should cap player level at 11-13 for balancing.

Entering legendary would adjust the scaling to 2/3/4/5, NK levels 14-17, and as you tier up, the scaling improves.

Single Player would be unaffected of course.

This would keep player incentive to level up their units to play in higher legendary tiers, as well as for Team Wars and single player, while absolutely and completely stamping out deranking for the purposes of using higher level units to win easy games for PVP card packs and events.

Ranked PVP would become a matter of skill, strategy, and deckbuilding, and matchmaking times could be shortened considerably since the matchmaking range can be safely widened without fear of THIS happening.

I highly doubt anything will come of this, but I believe that this is the best option for the health of the game. It is painfully clear that the Pay to Win model the game uses, pisses everyone off.