Well I think some more or less standardized equipment is on the way and I guess some people will work on it after the 3CB Equipment Mod is out.
Especially the DMS is supposed to go on marksman-rifles and I never really had problems with it.
In regards of optics in general, here is a simple explanation of how different scopes work.
Mil-DotThis is more of a system for sniper optics and I dont recall seeing a scope
that is using mil-dot optic with a combination of a red-dot or something
like that. However I think it is not bad to know how these actually
work.
Looks pretty simple and if you have no idea what it is about, it will probably leave you confused.

To make them work you have to do a bit of math, but it is nothing
complicated and thankfully every person in ArmA 3 is 1.80m tall. So what
you do is cou get on target and see how much mills the target covers.
Then you do a bit of math and you get estimate the distance to the
target and range your scope accordingly.

You can shorten this calculation by just doing 1800 x covered mills.
PSO type scopes
My personal favourite because you baretly need to zero your scope and finding the range to the target is a bit
easier. Here you have the scope.

In the middle you have bullet drop compensator marks. The only difference
to the one you can find a ACOG or the LDS is that it doesnt show the
meter marks. At the bottom of it you have a rangefinder that works
similar like the mil-dots. The main difference is that it will do the
math for you.

You get your target in sight and make it fit into the rangefinding scale.
The number show ranges from 200 - 1000m and so you simply have to check
the number and you have the range to your target. Combined with the
bullet drop compensation marks you dont really have to zero your scope
most of the times.
Bullet Drop CompensationThose dont allow proper rangefinding inside the scope, so you need to rely on
your skills to estimate distance or you haveto guide yourself in. Pretty
much all of those scopes on the game (as far as I know) are zero'ed in
at 400m. Like in the other scopes the numbers each represent 100m. So
the 6 means 600m etc. If you cant really estimate the distance to the
target you can at least shoot it and adjust your fire on where the
bullet actually landed.
