Yes, Maws can swallow MkV ships but how long before another MkV ship pops them and releases the swallowed load? They are extremely vulnerable to bombers, similarly to anything with heavy/ultra-heavy hull, which is most of the really useful stuff - Id really like to see some hull switching for the high-end stuff. Everything being Heavy/Ultraheavy just makes bombers much more ridiculous than fighters/frigates.
For me, Maws are amazing at the beginning when you can just send 3 of them to planet near your HW and clear it by themselves. Later on, when waves start approaching hundreds, their usefulness diminishes. If anything, Id like to see the swallow rate sped up, even at the expense of lower swallow cap, I never fill that up anyways.