I've done all the mini battles (except for Ramuh), they were absolutely awesome.
Back when I was a beginner Summoner an LS told me that they could help me get Ramuh, and said I could still do the mini battles.

I guess either I understood them wrong, or they understood me wrong, but afterwards I was saddened to learn that in fact I couldn't do the Ramuh mini-battle after all.
But the mini-battles that I did, the memories of those are very precious to me.

And even today, the most interesting job (and almost the only interesting job) on FFXI for me is Summoner.
When I get rid of the Perp with the Caller's Attire+2 gear, I'm so taking on the original primes one by one, just for the lulz.

In any case, I agree, the mini battles teach a summoner a lot. Heck, you learn one of the most important things, and THE thing Summoner is great at: Kiting.

Your avatars aren't nearly as strong as some pets of BST and or a PUP's puppet, so kiting becomes the thing to do to beat stuff, and so far it's worked great with many battles I've had.