Yes, MB is powerful. But it's not the 'lone slayer of fleets, stalking the map at will, snuffing out the hopes and dreams of millions, against whom resistance useless' people are making it out to be.. Over-powered ? I don't think so.. for a few reasons.
First, it can be interrupted. It's not instant damage. It takes a while to do 'all that damage'. You can drain anti-matter, use an ability.. or <shock!> RETREAT YOUR SHIPS FOR 20 SECONDS ! The Marza doesn't move when using this ability. Yes it can kills hundreds of frigates ( the most nimble ships except scouts ), but they can also run the fastest.
Second, cruisers are not killed with MB. Hurt, yes. Not killed. You can retreat and repair them. Same for caps, but even more so. So, yeah, all your LRf's are toast if a Marza gets close. Not en entire fleet.
Third, the Marza is a game changer, but it works both ways. If a TEC players gets a Marza to lvl 6, it took a lot of work. Work that can be erased with a bomber swarm. Any idiot that COUNTS on the use of a single ability to win the game isn't any different than the idiot that spams LRF's, LC's, or HC's. So, if it's GG when TEC gets a lvl 6 Marza, does it work the other way when it goes 'boom' ?
Every race has some ability thats OP'd.. Want to talk total BS ? How about the Vasari ? With phase stabilizers they can concentrate their entire frickin fleet and have it ONE jump from ANYWHERE ! Add in a Kostura cannon, and they can bypass 100 choke points, my entire fleet and attack my homeworld in ONE jump ! Supply lines ? WTF is that to Vasari ? One planet ( or two ! ) with four or five frigate factories and they have 'insta-fleet' anywhere on the map. Advent ? Big deal if they loose a level 10 cap with all those synergistic abilities, they get an automatic 'do over' with the ressurection ability. It's worse than Jason in the Friday the 13th movies.. they just don't stay dead. Granted, these things ain't free, and they take some work, but so does getting a Marza to lvl 6 and keeping it alive.
It's a game changer. Dangerous, yes. Knife's Edge, I believe it was described as.. When I play, I damn sure keep an eye an a lvl 6+ enemy Marza. You have LOTS of options to counter it : AM drain, dis-abling abilities, tactics, retreating, kiting around the gravity well, burying it under a wave of bombers.. In ONE tactical situation ( the middle of a pack of frigates ), IF it has the AM, and IF it survives to get there, IF your opponent can't dis-able, IF the enemy fleet is staionary, and IF they don't run away, a Marza is death on a stick. So, if you insist on driving your fleet up next to one, parking it, and not paying attention, then yes, your'e dead. Other times, considerably less so.