Wound Allocation in 5th

Wound allocation doesn't work in a sensible, clear or common sense manner in some scenarios. I will try to explain how it functions and indeed how this could be fixed relatively simply.

Scenario 1. Ten Marines with bolters vs ten Marines with bolters.
10 shots, hit 7, wound 4, four models make saves, the player who has been shot removes any three models. That is nice and simple.

Scenario 2. Ten Marines with bolters vs three marines, two with bolters, one with a special weapon
10 shots, hit 7, wound 4. Wound allocation fun time. You allocate wounds per group of identical armed models. Eg in this scenario you can stack 3 on the bolter guys and 1 on the special weapon, or two on the bolters and two on the special weapon. Spare wounds do not transfer from group to group. So if the bolter guys fail 3 wounds, the spare wound is lost.

Scenario 3. Ten marines, plasma cannon, plasmagun and bolters vs five marines, 1 with plasma gun, and 1 sergent.
This is a more likely scenario and can get complicated fast.
Fire plasmacannon first [as it has more targets to hit at this stage] and hits 5, wounding 5. Plasmagun wounds 1, the other marines bolters inflict say 4 wounds.

So you now have 6 plasma ap2 wounds, and 4 boltgun wounds at ap5 to divide between the 5 models. However, there are three model groups which makes this complicated.
You could for example. stick all 6 plasma wounds on the three bolter models, and put two boltgun wounds on each of the special weapon and sergent, meaning the two more valuble squad members could survive! Notice if you didnt fire the bolters, you would have killed the whole squad. Also if the five man unit didn't have different types of models, they would also all have been wiped out, regardless of the bolters firing or not.

The best way to avoid this problem is to pick weapons that have complimentary ap values. Eg all low or higher than the armour you expect to go against.

It is worth noting that some units can be built to specifically take advantage of this rule. See nobs bikers, space wolf rider things which can both take every model with different gear and they have multiple wounds meaning that the unit can take a huge amount of wounds before losing any models, greatly increasing its survivability and death dealing potential.

My Leman Russ tanks never fire their heavy bolter(s) if enemy in power armour is out of cover. There is no point as it makes the enemy have a chance of saving. It is ridiculous but true that firing more shots means people have more chance of survival. If you really must fire the fore mounted gun, upgrade to a lascannon.

As long as you dont play against people who specifically create these rule exploit units, the rule functions fairly reasonably. I can see why they have done this, but the fact the rulebook itself expressly shows how to use the wound allocation to keep men alive suggests to me GW knew exactly what they were doing when they put this rule in.

The simple solution to this problem would be to just remove any models who take wounds from weapons which cause no save, before wound allocation is applied. That way should the even from scenario 3 occur, you would remove up to six models from the plasma cannon allocated as per the normal rules, then allocate the remaining bolter wounds. In this example, you wouldn't need to allocate the bolter wounds, but if the squad was ten models strong you would. That way you would not be penalised for causing more wounds.