Given the current state of the game, you are correct.
The advantages to running a mono-color (or at worst a dual color setup using the class’s secondary color) are so significant that running any of the off-color Class utility spells are a major detriment to the player, unless that utility is extremely potent (only such effect that might be worth it is a spell that features Blind currently, as not every color currently has such a spell).
I keep waiting for some kind of rebalancing to occur regarding mono-color setups, because the double/triple/quadruple mana generation from a single match is overpowered, absurdly so when running a loadout of 50 mana spells that can filled up with a single 3-match with sufficient mastery (4-match otherwise).
IMO, I think they were trying to channel players towards dungeons, especially as there is Easy mode now [which can be a bit of a misnomer for newer players] to give them additional purposes to be run beyond specific armor drops.
Hard to say, as the devs tend not to be publicly forthcoming with their underlying design decisions, especially when they involve progression walls and monetization.
0.35 added a whole bunch of progression walls to the game, and left all of us waiting until the 0.36 to see what the intended hoops the devs expect players to jump through are to clear those progression walls.