It is a pleasure that it helps you to consider these powerful Gladiators.

Do you think investing Glint into Merits is worth it long-term, or is it better to focus on loot chests?

In my opinion, merits can be bought up to 200 merits for 450 Glints at the maximum price; the latter ratio is not viable as you need the rebellion reward card also. Personally, I don't buy merits when the price exceeds 300 Glints per 200 merits in the shop.

And for the MAJOR CHEST at 1000 Glints, you can have 500+ merits, which is a far better plan for merits, and you can also have the chance for other assets. I do it for my approach, I hope it will help you to figure out your own strategy.
Thanks for your comment. Have a nice day.
!PIZZA
!BEER