In my view, T2 is the best tier level. It has a lot of tactical options, but very little cheese like fast nukes or fast ahwassa. IMO, all tech 2 factories - tech 2 land particularly - should have reduced price. Say, 700 for a T2 land factory hq, maybe 500.
The problem with the current balance is very little T2 is seen. It's usually workable to simply build some T2 defense and hold the line until T3, or simply upgrade the ACU build suite and build land experimentals to defeat enemy land (no factory required!).
T3 is probably the right price and should stay put. Just make T2 easier to spam.