Good thinking to buy more rare draws to upgrade your summoners. I have all mine at max level, but otherwise, that's a very effective way of getting high-level summoners.
I'd also like the choice between GF and RF. Matt said it will probably be added in the future.
As for legendary draw and the burn value of the cards and the discrepancy, yep, you have a point, but also, the benefits of leveling up legendary cards (or even epics) usually outweigh the cost differential of drawing the legendary card(s) you don't want/need. At least in time, through their increased stats and abilities in the gameplay.
I wasn't opportuned to max out my summoners before the changes happened, it's quite saddening that I wasn't able to. I have them at level 5 and six and it's definitely still a long way to max level. I think they're more priorities than anything at the moment. The summoners at the moment, then I'll do the remaining upgrades of the other cards.
It is a good chance for you to level up one set of summoners as high as possible, without buying them from the market with DEC. So yeah, push it! If you have more Glint than for 100 Rare Draws per season, I'd take Batch 2 as well. The fact that you don't have any higher-level summoner affects your potential results (provided you have or plan to have cards that could be played at a higher level).
My summoners first, then I hope I get more Glints to actually compete for legendary draws.