We don't even do legendary tasks, but I have to say getting random minors is pretty silly. Everyone at the endgame post guild patch can attest that the problem with minors is not a lack of minors on the whole but rather just red due to both them being the most required and least dropped minor (in PvP, where you are mostly likely to spend your time if you are doing legendary tasks in the first place). Even then, the gold key glut and their release pattern of not putting out minor red troops in a while is already closing this gap, and most everyone completing this task more than likely has a 83.3% chance of what amounts to a null drop when minors are rolled, if the minors are of random colors (and approaching 100% for many).
I know that I've never done a legendary task and play much less than many of those completing the tasks do, but in checking what I have/need in terms of minor, I'm at least 200 over for every single color except red (over 1000 over what I need in the case of yellow), with red being 700 under. That being said, I also have over 24,000 gold keys saved, which is likely to cover that need completely for the foreseeable future.
Lets look at it another way - anyone doing legendary tasks gets at least 670 gold keys per week. Gold keys have an approximate drop rate for minors of 18.8%. You get approximately 126 minor per week, just from the first 6 levels of the brown guild task. Just stopping there, that is generally more than the total amount of minors required to trait anything released in glory packs, especially with our average number of troops per week having gone down. Now, only about 21 of those will be red, and you are probably bottlenecked on red now, but if they continue their color imbalance corrections with releases, eventually, you won't be. Even if they don't, you also get three minor from every glory pack, which mitigates the minor cost on whatever color that troop happens to use, largely nullifying how many extra minors you need to trait new glory pack troops - the exception being doing if they did something trollish like releasing nearly an entire kingdom that nearly exclusively uses red minor without event packs, or releasing a bunch of consecutive red minor troops back to back. All that is completely independent of any battle drops (though, usually, not much significant here as your highest number - yellow - is primarily what you'll gain), gold keys from tributes, or legendary tasks. In all likelihood, even without the legendary tasks and battles, you are moving toward not needing minors of any color, ever. Getting minors from legendary tasks would be about as pointless as getting souls in the long term.
If anything, straight up gold keys would make more sense than getting minors, because I'm sure a lot more people need to ascend one last common than need minors of every color (and the gold key can still get you said minors, albeit at a slower rate). And needing approximately 20000+ gold keys (a number that continues to rise with each common release!) to ascend the newest common all the way to mythic, you are less likely to permanently outpace the release schedule, as is now possible (and likely) with minor stones.