For all the Executioner F could be called a sniper . . . yeah, I danced against the 3 Warhammer 6Rs which had about 300 BV as a advantage. Yeah, it was against the bot but I basically played in a stand of woods on a hill and broke down the 3 Warhammers; running, MASC/SC and jumping. Using double blind, the woods could break LOS which helped me out when I would re-emerge into their sight. Run along the woods, duck into light or heavy and fire at a Warhammer. Jump over 3 or 4 hexes to be in heavy woods, keep firing, and then depending on heat & init I could jump behind the thick part of the woods to break LOS to the Warhammers . . . not sure what the Bot decided to do, but when I popped back out one turn I had a back shot on one of the two remaining Warhammers.
I am not sure the brawler set ups are still not useful, but probably not for dueling. I think, in a meta/war environment they would be used as linebreakers. If I am putting a force forward in a thrust to break a enemy defensive line, sending in one of those brawler configurations- like the Executioner D. Get it close enough that it can rush the line and unload- it's weapons and particularly the SRMs can cause disruption to pave the way for the rest of that force to breakthrough. Is it perhaps a suicide mission for that Executioner? Sure, but that is not as much a problem among the Clans as it is the IS.