I'm not necessarily disagreeing with you, the best I will say is that they could potentially salvage something from the playstyle of DPS BLU, but you do run into a few problems that the devs have stated as their lack of desire to make a "full" BLU. With an full BLU, do you need to learn the spells? Would I need to go out and collect the primal spells and everything else? If not, how do you justify the existance of both limited and unlimited BLU. Now if it was only unlimited BLU that existed (Highly unlikely right now), do we have a SMN problem where most of the iconic spells are gutted? The other option is gating unlimited BLU behind limited BLU, and I think that would cause more complaints than it is worth. I'm not saying you are wrong, I just think it's far more complicated and messy an implementation than is said here.
Learn rates are non existant now, and only serve as a motivator to run content synced. I like the trade off and it makes running synced extremely viable, something that I have been clamoring for since heavensward launched. For reference, learn rates are 100% if you run content synced.
I will agree to an extent about the repeats. The real difference comes from elemental affinities, which is something I would like to see expanded upon in the future, condensed libra is a start, but these skills are mostly designed for the masked carnival right now.
I completely agree with you and there is a place for duty finder content in the current implementation of BLU (sorely needed too). Tying duty finder to the BLU log would help people find the parties they want, and awarding bonus currency through a BLU roulette would make running the content a lot better. I know thats not what you are asking for, but I'm just showing how the current implementation of content can support this request. Oh, and this becomes even better if BST becomes a limited job because it would be a roulette for both BLU and BST.