Good places for SP farming?

Typically when I need SP and there’s no easy maps (or TTs) to farm SP on I just run through the 8th stratum of the training tower a bunch of times, ensuring 5 enemies each run and usually doing it Friday-Saturday for double SP. The mini TT will be a gold mine if you run a healer (let her heal anytime you can while keeping her out of danger, or let her attack and kill when it’s safe to do so). Another solid strategy which has worked wonders for me is to train lower level units and let them constantly be in combat, and let your healer heal them after combat (you can build fast SP for just a few stamina points if your training unit isn’t strong enough to kill everything on lower levels). I ran both strategies with Elise and Priscilla, and they have worked wonders.

Well, Warrior's Maps are over, so the best way to farm SP is probably the Chain Challenges, or at least for level 40 characters. I usually bring a character I want to SP grind for, a healer, and two dancers, or 1 dancer and a back-up unit in case the main SP character can't kill a unit.

As far as healers, there really isn't a "good" consistent way for them to earn SP, at least not that I'm aware of. They're just too weak usually (Unless they have Wrathful Staff I guess) and healing only gives them like...1 SP? You can always try the Pain+/Savage Blow x2 method. Have the enemies take 21 aoe damage, then finish them off with your healer.

If it’s not too late and you haven’t cleared this mission, this is the best spot. Chain challenge 1+2 on normal. It’s very easy to clear with level 40 units, take along 1-2 dancers and a healer to focus on your main unit.

The most important part is to make sure you surrender on the last stage. This will allow you to repeat it without getting reduced SP because it’s already been finished.