i think you misunderstand why tyranny is good

with most other government types, when you attack at max efficiency (less than 1/3 of your unit type total) you lose 1% readiness but it takes 2 turns, and running a turn doing anything except a GS, BR, PS, SS, or AB, gains you 3% readiness, so you can get of a large number of hits in with a minimal amount of readiness loss

with a tyranny, it only takes 1 turn to attack, but you lose 4% readiness at max efficiency. so you have a lot of turns that you need to use to regain readiness, this is where missiles, teching, or building and growing comes into play. you can still put out a large number of hits, and have turns to do other things. with the other governments, you dont have as many readiness turns to accomplish other war goals outside of hitting.

tyranny: 44 turns hitting at max efficiency for 19 hits and regain back to 100% readiness. that is 25 turns to launch missiles and build or spy

other govs: 44 turns for 19 hits and regain to max readiness, but you only had 6 turns for things other than hitting