No one is doing these tests against other capital ships for reasons. Onslaught is basically a meme ship at this point around here.
That's because no other capital ship is explicitly built, for meta and in-game lore reasons, to bring devastating firepower to bear facing forward while being vulnerable to the rear. So people can look all cool and awesome, "look at me, I outflanked the ship that is expressly designed and described as something not to be used solo, but in a fleet setting!"
The Onslaught is the F-35 of Starsector; the one ship everyone just loves to complain about. I remember a year ago trawling through the forums and marveling at all the people complaining about it. "Guys my Onslaught build is 10 flak cannons 30 Vulcans and 3 offensive guns, OMG this ship is terrible!" This thing is Sajuuk. You bring it to
bear. It's not a complicated concept.
And speaking of bringing to bear, the Onslaught has pretty good firing arcs on the sides, or at least it did in 0.91. It doesn't take every gun in the broadside to make a frigate bug out; esp. when it's so fluxed from shield-tanking shots that it hasn't much left to shoot with. The only anti-Frigate tactic you needed in 0.91 is "fire as you bear." The gun arcs were nerfed a little but so was the maneuvering penalty of Heavy Armor, which more than makes up for it. To say nothing of all the
other buffs it got.
Ballistic Integration and more flux-efficient pulse cannons!? If this keeps up I'm going to make an Onslaught bingo chart.