One of the usual points for taking them is their low cost - 85 points give you 5 scouts with a meltagun, your most basic setup. Don't even get me started on things like camo cloaks, missile launchers or even bolters, because that is not why you want them. They are taking a precious elite slot (or 2 if you like redundancy) and with the toll Wolf Guard slot means it's either Scouts, or Lone Wolves, or maybe a Rifleman Dread. I wouldn't waste an elite slot on a small home objective holder when you can just have 5 GHs with a Razorback. The Wolf Scouts are in the Elite section, and for a good reason.
Common loadouts5 Scouts with meltagun, 85 points
Cheap and cheerful, they have the minimum they need to do their job. If you're very short on points this is an acceptable loadout, although for a few more points we can dramatically increase their damage input as we'll see now.
5 scouts with meltagun, wolf guard with combimelta 108 points
So what does the extra wolf guard offer? well quite a lot: a second melta shot to reduce our chances of blowing up that manticore / predator / dreadnought, 3 more attacks on the charge, a 3+save and Ld 9 (which you will most likely need!). I'd say this is the standard loadout and the best points per value, as you have a better chance to a) blow up tanks and b) tie up infantry.
5 scouts with meltagun, wolf guard with combimelta and power fist 133 points
Starts to get more pricey for a suicide unit. The added fist helps if we are to charge a vehicle, or sometimes multicharge a vehicle and a backfield unit. Usually in this area you won't find CC specialists, bur rather a bigger unit like 10 devastators or 30 guardsmen, so the fist comes really in handy to ensure yuo get away with a couple more casualties that could decide the combat - and if you win, your opponent will likely run off the table.
Some people purposedly load out their wolf guards in a flexible manner (combi-melta, combi-melta+fist, combi-flamer, wolf claw...) to ensure that whatever the army you are facing, you have the right tool for the job. A couple of meltas won't do much against a 30-men IG blob or Lootas, but a combi-flamer and potentially a mark of the wulfen could be devastating. Or a multicharge with melta bombs to a tank squadron. I don't take it this far but I always have the choice between a PF toting or CCW wolf guard with a combimelta.
How to use themEasy as chips - you basically want the wolf scouts to appear behind some enemy's arse and blow up an expensive tank, or at least tie a backfield unit like devastators or IG platoon. Their 3 attacks on the charge and WS4 allow them to assault most units in there, although don't expect them to come up on top very often due to their low numbers. Making the squad bigger has its own issues, like the cost increase or may impede you to charge as you can't fit that many bases.
If you are lucky, they will show up on a 3+ on a board edge of your choice and wreak some havoc. If you are not, and this seems to happen to me more than 33% of the time, well they might still have a target or objective near by, or in the worst case there will be nothing for them to do, you will forget about them and not pack them when leaving (yes guilty as charged).
Endgame and flexibilityIt's important to identify the key threads you
And a final note - my first impression was rather negative, with the scouts appearing nowhere near or when I needed them, even when fielding 2 packs of them. My expectations were just too high. Now I don't rely on them anymore, and think my strategy as if they were not there. If they appear when and where I need them - great, and if not it's not affecting my plans. Everything has worked better since I approach them this way, and I have to say their performance was great in the last couple of tournaments I attended.