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Well, Gauss weapons got hit pretty hard. Glancing hits can no longer outright destroy vehicles, even on a lucky roll, meaning you now have to take Warscythes/Heavy Destroyers in order to reliably take out heavy armour.
Sweeping advances after combat will also annihilate Necron Warriors due to their low initiative.
Other than that, I think the Necrons are pretty solid still. The Monolith is now a bit more useful because many armies are going to have a hard time taking it out. I'm still having great success with the 'crons!
i have been doing better almost now the 5th cleared out a lot of house rules we had that made it worse to play but now i love it the monolith stays right in there face and takes everything they trow at it. now in hand to hand i have always servied i just get stuck fighting till i die well now with the monolith i suck guys up and put them right where i need them to rapid fire on them.
i think necrons are even better then 4th well except for the sweeping advance but a monolith is very tough now i almost always use one
Necrons are still a very solid army, 5th edition wasn't an extremely detrimental thing. The gauss getting nerfed was a hit to the army, but the Monolith (which I don't use, oddly enough, lol) getting beefed up was a welcome addition. Honestly, fluff wise it makes more sense for guns that flay atoms from a tank to take more than a few shots to destroy it (though immobilization makes sense, and I can normally get that from a decent volley), and along that same line it makes more sense that a Monolith should be the hardest vehicle to kill in a non-Apocalypse game.
Welcome to 5th
The newest rule did hit the gauss hard i have a hard time with tanksnow, but the lith added a new tatic to my plans. the guys i play with hated and i mean hated the 9 deystroyers i used to run in my 2000pts list now we are playing 1500 so i went down to 6 heavy destroyers and i asked sould i try the monolith i have alwasy had the modle just never played it just like my Nids titan i have and they said yes now they hate that more. i have only had i blow up once to a very lucky lass shot. other then that nothing has happened to it. i do love that thing now.