I like the summoning, because with the BW and the COGS, I summon an Engine turn 2, and for a 1k list, it's a huge impact. So, in these games, I use my skinks, either the 10 block or the 30 block (it depends of the game) to protect my slann. And while my opponent, was occupied at charging my skinks but not fighting them (thanks wary fighter ), my slann stack up some conjuration points and turn 2, baam ! An engine ! During that time, my ripper take out some key units and even survive well.
Yes, really well. I was gladly surprised that I succeed to use it somewhat correctly (I'm not that good yet ). But legion of Nagash is a real pain ! I kill, and kill and kill, but you know what ? It's useless because the troops come back to life, arkam heal himself a lot and so one. But that was fun (but I don't want to play against it too much ^^).
Arkhan List can be rough. I normally try to kill necromancers first when playing against a Legions of Nagash army. Rippers can definitely take Arkhan out when in Shadowstrike, but is rare that an opponent will leave him open.
I used my rippers to take out the engine mortis because of the battalion. The necromancer was hidden behind some skeletons so I couldn't take it out. And I use my 30 skinks to inflict some good wounds to arkam but he healed himself too fast.
Heros are key for a Legion army kill them as fast as possible, Arkhan is a beast if left to cast his spells.