if you're going to fight boss, dont even try SAM/RNG, with cap archery merit, sushi, max racc gear, the acc still sux, and when u do land sidewinder, it's prolly gonna be lower dmg than GK WS.
I've only tanked LAC and Battleclad chariot with SAM/WAR, it's pretty simple just use seigan+third eye wearing normal TP gear, when third eye is down switch to -phys, when the chariot is debuffed (slow2+elegy+para) it's pretty easy to tank them. I have not tank LBC yet though, but i'd imagine it'll be pretty easy to tank that also as SAM/WAR if you killed 10/10 gears. As for Armored chariot you'd prolly have to /NIN and get hate straight from your dmg, since mortal revolution will pwn your third eye.
SAM/WAR Polearm > SAM/RNG all the way
Penta Thrust + Overwhelm = teh sex