13 termies would never make it while losing that many a turn. Remember that reapers can move and shoot. Also if the termies deepstruck the army would be tabled turn 1. Since the reapers can move and shoot means the termies will get into combat with maybe 2-3 units before the end of the game, maybe.
Also as someone said the all reapers list gets worse as points go up, thats why i built it at 750.
*sigh* You are going to make me mathhammer this, aren't you?
At 750pts you get Belial and 2 squads of 6 Terminators with a split firing Plasma cannon. Terminators are automatically deep striking turn one, so regardless of whether or not the Reapers have first turn, the Terminators are shooting first.
Deathwing Turn 120 bolters
= 13.33 hits + twin link
= 17.77 hits
= 11.85 wounds
= 3.95 dead
2 Plasma cannon shots
= 3 hits
= 2.5 wounds
= 1.67 dead (assuming you are in coverwith the twin linking, figured that scattering a bit to clip two models can average out to 3 hits)
Total dead Reapers = 5.62, round to 6 dead
Reapers Turn 1Starswarm missiles give you the best numbers of killing terminators:
36 shots
= 30 hit
= 20 wound
= 3.33 failed saves, round to 3
I say failed saves because there is a good possibility that wounds will be allocated to Belial first, and he will always take two before using LOS to pass them off. At best for you, you kill 3 models, at worst you kill one.
Deathwing Turn 2Now the kicker here is how the army would be deployed. If you have squads close to each other at all there is a good possibility that you will lose three on the second turn. Belial's squad will have deep struck and not scattered within charge range of as many units as he can reach. If possible, he splits off from the squad to chase a unit down, the remainder of the unit shoots at a smaller unit while split firing a bolter to charge a closer unit.
I can go into greater detail, but at this point I am tired. But do you really think the Reapers can out attrition an army with a superior save that shoots almost as well as the reapers do? Not to mention the fact that the Terminators can and will charge into combat and will win those fights. You are already down two units at the start of the second turn, and there is a good chance you will be down another three units by the end of the 2nd turn.
Turn up your nose at Terminators, but until you have been on the receiving end of the Deathwing, you are always going to underestimate their capabilities. This is coming from a Deathwing player who regularly fields 26 terminators at 1850. A large number of terminators for a certain points value on your door step turn one are always hard to deal with.