There is some major balancing issue about the stronghold fleet yes, and as already mentioned, the SLF kill giving more merit and less bounty than killing a normal powerplay ship is a primary concern, at this pace the fortified only gonna become the meta given how stronghold having a fleet are easy to undermine.
In fact I honestly wonder if the dev did have tested stronghold fleet defense in a fully engineered ship sometime

Stronghold fleet should represent a real challenge for a full wing, which is absolutely not the case atm.
Speaking of undermining, I have even more concern for this
https://issues.frontierstore.net/issue-detail/67329 and given that I see one very specific power capable to produce more than 50k undermining merit PER system update in most of the enemy stronghold system arround its space, I have very little doubt that this exploit has been mass used.
And I just saw one with nearly 80k undermining merit dropped in one system update, a new record...
And please FDev, next time that you are making an update of this scale, do an open beta as I'm sure the community will do a fabulous job into finding bugs and balancing issue, don't let the beta testing work to streamer, there primary job is to entertain (and most of them simply focused on the Mandalay, not PP 2), they are not beta tester...