I was assuming these dragons he made were small enough to fit in the place he summoned them, and so they're not actually that big. If they were such huge dragons that they busted through the walls and ceiling when he summoned them, I would have hoped Windel would have mentioned that.

So, yeah, Tia Yang can totally take a horse sized dragon golem. Especially one that is entirely immobilized!

Also, Tai Yang was being considered for the teacher in charge of teaching the students how to fight.. so, that too. He's mainly a student because he needs to learn how to survive in the modern world, not because his fighting power needs to be amped up further.