I use blast shield on most of my classes, especially my rushing ones, it doesn't restrict your view it just makes c4 and IED's into water balloons
Much more helpful than sitrep IMO.....sitrep protects you from a few explosives, blast shield protects you from much more. One thing it doesn't stop is danger close c4 and rocket launchers, so beware of that.
As for the class help...I use really weird classes so I can't help much My most slayer ones like yours would be LSAT with red dot, grip and muzzle brake uses attachment perk, quick draw and stalker, that is my main slayer class, It has crazy TTK, accuracy and range, out damages nearly all assault rifle users I encounter on large maps. (Or I use the honey badger with grip and extended mags, quick draw, stalker, dead silence/awareness and marathon for smaller maps where a silenced weapon would be smarter than a loudass LMG.
I generally don't use lethal/tactical unless I'm using a riot shield, sniper or shotgun class. And marathon on this game is amazing, the maps are big as heck, I use it on nearly every class but my LSAT. Also try to not use silencers on your ar/lmg for big maps....Have at least one non silenced gun for big maps, and at least on silenced ar/smg for smaller more rushy maps. One other thing, a secondary pistol is much better than any one point perk or lethal/tactical IMO, having that secondary saves me a lot more than the small perks. So if you have one point left over try a handgun
My most successful classes are a bit different, but fun and effective if you want something different than standard slayer classes. There are two main classes, my rush class which uses a shotgun (bulldog yes I know im gay for using this thing) and the riot shield class.
The rush class uses k7 SMG with grip and extended mags (I find it the best smg, good silenced range and rate of fire, better hip fire IMO) or the bulldog shotgun with muzzle brake and extended mags. ( this gun is OP, you feel like a cheater using it but it puts up some nice scores haha) you can however use any shotgun or smg with 2 attachments for this setup, k7 and bulldog are just my favorite. Perks for both smg and shotgun are the same - ready up, marathon, blast shield, steady aim, dead silence and amplify.
My riot shield class has two variants, one is a more traditional riot shield that I have been using since mw2, the other is an overkill one.
Normal riot shield uses whatever attachment you prefer (they all have strengths and weaknesses) secondary is dual pistols, I like berretta's but any will do....just no .44's. lethal is either throwing knife or C4, their both amazing just different ways to kill people. Perks - reflex, extra lethal, blast shield and steady aim. The overkill riot shield uses an overkill bulldog with muzzle brake, c4 or throwing knife, perks - reflex, blast shield, overkill and gambler.
I also have a sniper class but I suck at sniping so I won't post that garbage