That is the only way to fill all temples, it's great if they can have 50%, 70% discount in shop.
one thing I notice is a few redundant (hero) classes that waste temples buff. Rogue and Necromancer are 2 obvious redundant classes, dev should merge Rogue and Necromancer to Sage, as Sage is a messy class. Buff for Necromancer and Rogue change to Faster Build or Army Cap.
Another thing is some temple buffs are useful for 1 race but useless to other 3 races, like buff for Monk. If the game is designed as research unit 1, 2, 3, 4, 5, 6 are same when switch races, temple buff should change to 10% for Unit 1, 10% to Unit 2 ... of all races.