We will definitely try, the goal (which is very difficult and something most games struggle with) is to keep them balanced and give unique passive abilities to all creatures, meaning that they all can be used in competitive high-end gameplay. Now of course this isn't completely realistic and some will always be left out but we believe it'll be more of a patch-based rotation. For instance, some of these starters here may not be great in a certain time period but once more creatures, healers, items, come in or changes occur within those things they may see a comeback in how required they are and demanded by competitive players.
In most games it's usually a very small percentage that gets used at high-end levels, but with the way rarity works and how extremely rare it could be to get a max stat creature we may see some higher stat creatures that may not be great at even stats but still end up being surprisingly strong due to the luck of draw of players having encountered and caught them with high stats.
We do also have different restrictions for different ladders planned, like for instance at some point with more expansions released there could be a ladder where only alpha creatures are allowed to participate in.
Thanks for the awesome answer. You answered more questions i had by explaining some of the thoughts behind what direction things will most likely go. Sounds like the planning behind the rollout is being very well done with much foresight. Really looking forward to seeing this all come together! The possibilities are endless!