Looked into
IA Apocalypse 2, it is generally right with that 4++, with a 48 inch 10" blast StrD barrage with "3 structure points" (translate into current Hull Points is 9
right?), and more bad news for you it is only 600 points. Are you taking Imperial Titans? If yes, even more bad news for you
that main gun ignores power fields and void shields, so one less saving measure for your Titan!!!
Now I think you have to accept that any vehicles and
MCs (such as Grey Knight Dreadknights) without a decent
inv save you put on the board is As Good As Dead when this thing turns its eye on them. Your only saving grace against this thing is try have a lot of elite infantry units jump from cover to cover, place as many of ruins terrain on the field as you possibly can, because even that mighty D won't ignore "toe in terrain" cover. Vehicles and
MCs on the other hand, can only gain cover save by 25% blockage of
LOS, which is ignored by the barrage rule. If you take flyers they are good in surviving that Super Heavy, but if your opponent is taking a couple Crimson Death formations then your flyers are dooooomed as well. Basically the only idea I can think about is have multiple Librarius Conclaves, each formation fish for Invisibility (may Emperor protects
) and form lots of "Death star" type units on the field, take down his WKs,
WGs and other stuff like D Cannons quick, and leave those Eldar Titan class stuffs. Even they are criminally undercosted, they tends to be relatively few in number, so you if you take out other sources of
Str D, you could loss fewer guys in late game.