I play against some pretty good eldar players and since it seemed plague marines might stand a chance against the pesky Harlequins I thought I might run the numbers and see what happens.

I assumed the harlies got the charge (as they almost always do)

10 in number from each side (point cost is about the same)

Plague marines get no upgrades. Harlies have kiss (as they always do)

I'm rounding numbers. 2.1 = 2, 2.5=3, 2.9=3.

I'm favoring attackers if models have a %50 chance to live.

It went something like this.

H=Harlies PM=Plague marines

10 H charge 4 PM die
6 PM attack back 3 H die

7 H attack 3 PM die
3 PM attack 2 H die

5 H attack 2 PM die
1 PM attack 1 H die

4 H kill the last PM

My method I realize favors the attacker more so on the table the marines might do a little better, but it was still worse than I hoped. I guess I won't be leaving my PM unaided to buffer against Harlequins. Though in rhino poping out for rapid fire would be a good thing.