I agree completely with Owen S’s observation that the 1 vs 2 cour comparison to explain why StrikerS has been off to a slow start is deeply flawed. In the first season, Fate didn’t even show up until the middle of the fourth episode while we had a relatively slow buildup about ‘Hi, I’m Nanoha Takamachi, this is my family etc etc.’ and then gradually levelling up under Ferret Yuuno’s instruction.
There appears to be a similar structure in StrikerS. The main new character Subaru has her back history and connection to Nanoha built up and, with the other three newbies, are being levelled up. Although we do know the members of the original cast, there is also considerable ground to cover, given that ten years have passed since the end of A’s (not counting the last few minutes of the last episode), such as the setting up of Hayate’s new unit - which isn’t covered in the A’s to StrikerS transition manga.
It’s quite hard to do the ’start in the middle’ narrative IMHO because although that was used in A’s, we have the same knowledge about the new characters as Nanoha. That’s not the case in StrikerS where the studio has decided that we, the audience, should be levelled up in our knowledge of the new characters to what the original cast members know. In any case, I have this sneaky suspicion that it’s a no win situation either way. Instead of complaints about slow pacing, the ’start in the middle’ alternative would probably provoke complaints of ‘Who are these people!?’, ‘What’s going on?’, ‘needs MOAR background’ etc.