The second scenario would really be: Entelonania is doing awesome, everybody add it in their team, so it become one of the 10 or 12 regular top dinos you see every single boring fights (as it is right now with everybody using the same 10-12 dinos since the last shuffle). And if Ludia ever decide to nerf it, everybody will ask for a reset/shuffle anyway.
The problem is not how often we get a boost shuffle. The problem is balancing ALL the dinos. As long as there’s only 12 top dinos, having regular shuffles, only mean that as soon as somebody can get one of those 12 top dinos to team level, they then simply join the 95% of the players who are all using the same dinos. Basically, the problem is that your Entelonania should not be a lot worse than others, or a lot better than others. It should be about as good as Cera, Gemini and the other top dinos. And then, Indoraptor, Spinoconstrictor, Stygi and so many unused dinos we almost never see played, should simply be buffed to that same top level, because even if there’s a shuffle every weeks you still won’t see them being played. What’s the point of having 250 dinos and a boost shuffle every weeks, if only 12 are being used most of the time.
I do think more frequent shuffles would encourage greater variety, especially if they occur at regular intervals, because selecting and boosting any given dino wouldn’t seem like such an expensive commitment. I would be much more willing to run something suboptimal and potentially fun, if I knew I could replace it in 2 months.
As the OP mentioned boost shuffles would also do a lot to drive coins use and purchases. During both shuffles I spent millions of coins levelling up creatures that I had been sitting on the DNA for quite a while because my “eight” were already set (because of the value of boosts, I’m not willing to have something boosted on the bench that can’t be used for tourneys).