1. Easy its armor 11. Second The scenario didnt say they were in a rhino so deal.
2. My mathhammer was swayed to account for a level of fun rather than pure math. If were going math yours is straight flawed. Heres the load out. 15 shots create 10 hits with BS 4, which makes 5 straight wounds because 50% of 10 is 5 not 4.5. If your going to change the math do the math right. You cant expect to have cover when you want it and not when you dont. So 1 dead after cover and feel no pain. IF your going to be like that.
3. You charge with the 4 plague marines, and "YOU" dont get to decide where I put my lords, I do since its a mixed unit and they are not all going to be deployed straight in the front and i get to consolidate into CC. So My MSS hit two of your Plague marines, making sure to hit the one with a powerfist since noone takes plague marines without. He fails since the average on 3d6 is 12 as does the other marine touched. So You charge with Two deamon princes who make Base to Base and I still get to shuffle around to make sure were all stuck in, so ive got on MSS on each. They each fail again because of HARD math, but to be fair one succeeds or I dont manage to get both MSS covering my flanks. Im nice like that . However Deamon Princes dont have grenades so they go last in initiative since were in cover. Two whole units of Berserkers trying to make it into the CC when im surrounded by two MC's and a unit of 4 plague Marines? Now thats way too out there...maybe one unit. Ill give you that. But at least one MSS touches a unit taking out 4 of your attacks and delivering more punishment to your guys.
So now math time, 8 Berzerkers throw out 32 normal attacks, In which 16 hit, in Which 8 wound, 2.4 or 2 rounded to the nearest (the way math works) fall. The MSS delivers 2 hits on your Berzerkers, both wounds since its S5 to T4 but youve got the best odds to not be killed since your sv is a 3+. so 1 dies after the math. Its closest to 1 after rounding.
Now the Plague marines deliver 4 attacks on the Lychguard / Lord unit. And 2 hit and 1 wounds which is saved. However 4 hits come from the MSS and 1.5 wound. so either way its a toss up. Lets go with 2 for fun. 1 armour saves the other feel no pains it, no one dies. But if one of those plague marines had a powerfist and they almost always do, then the math would go like this. 4 hits 2 from a powerfist. 3 wounds, 2 from a powerfist. 1 armour save if unlucky then saved from feel no pain. but 2 casualties do to powerfist.
Now in initiative order its the Necrons. 9 Lychguard and 4 Lords. 6 lych guard attack the MC's 2 on the berzerkers, and 1 on the plague marines, 1 Lord against the 1 of the Mc's, 2 on the Plague marines, and 1 on the berzerkers.
Plague marines result. 2 from the lych guard result in 1 hit and 1 wound from a S7 power attack, 1 marine dies. The 2 Lords throw out 4 attacks and 2 hit and 1 wounds, the wound is saved from a combo of armour and or feel no pain. end of Combat, 1 or 3 plague marines removed depending on powerfist and no casualties caused. (Overall)
Berzerkers result. 4 attacks from the Lych guard makes 2 hits and 2 wounds, from power weapons so 2 removed. Lord delivers 2 attacks 1 hits and 1 wound from which its saved. Berzerker with power fist retaliates with 4 attacks hitting with 2 wounding 2 and two necrons go down. End of combat 3 berzerkers and 4 necron fall (overall)
Monstrous creatures result. The MSS that worked doesnt do anything but cease his attacks wince hes not in a unit. so only 1 Lychguard that inst touched by 1 or more different units has to attack, attacks the MC. with 2 attacks, 1 hit and 1 wound, and 5+ invulnerable is unlikely so doesnt work, MC takes a wound.
Monstrous creature that can attack but moved thru Difficult terrain and doesnt have grenades has to wait for I 1 before attacking. So 5 Lychguard and one Lord attacks. Lychguard send out 10 attacks, 5 hit, 4 wounds, 1 save from the invunerable. Lord attacks with 2 attacks , 1 hit. 1 wound. Deamon lord saves. Deamon lord retaliates with 5 attacks which 3 hits and 2 wound, 2 necrons fall. Demon lord 2 Necron 3 (Overall)
End of combat, Plague marines must take 1 or 3 extra saves for loosing combat.
Berzerkers win by 1.
Both MC's have to save against another wound.
Six necrons fall of which 3 get back up. 6 Marines fall, none get back up, and 4 wounds delivered to the Mc's
Round two will utilize the MSS again and each of your units will lose attacks due to not charging but the Necrons will yield the same number of attacks. If you cant win with the advantage, how do you expect to win when we are on even ground?