@ftxcommando @Haachamachama i now tested battlecuiser(bc from now on) with 1 shieldboat, under the conditions that the bc with the shieldboat have to close in to a broadside position bs, the bc only closes in enougth to use its main weapons, not its torpedos(20dps) both units were unmicroed aside from stopping the shieldboat from hiding behind the bc, plays out as follows: when the battleship does not kill the shieldboat first it blinks up a second time makeing the bc win any matchup. when the battleship targets the shieldboat first the results are as follows: cybran bs loses 1.6k hp left on bc(8k mass bs vs 8.3k of bc and shieldboat), aoen bs won 3.3k hp left (9k mass vs 8.3k), seraphim bs won 2.8k hp left [in this test a volley of the bs hit both the bc and the shieldboat but i didnt wanna redo, it just shows how close this is](9k mass vs 8.3k), uef bs wins 4.8k hp left (10k mass vs 8.3k).
this test is setup in a way to give the bs every feasible advantage in a direct comparison(full dps from the start, range advantage and even cost advantage aside from cybran), ontop of that any micro will benefit the bc since its guns cant miss while its realistic that the faster smaller bc can doge some projectiles since all the bs have relatively slow ones. make of this info as you will but to say that bc+shieldboat get beat consistently by any bs is straigth up not true.
edit: anyone is free to repeat this test and counter my results but your "experience" is more biased then any test i can make