True this. I spent a lot of time with the HK21 in Blops 1, and whilst I used SoH it was more for the quick raising of the sights than for reloading. If the amount of bullets in an LMGs clip isn't enough for you to give yourself some breathing space to reload, you're doing it wrong. I was fairly mobile, but I tried to keep most of my gunfights at range, where the gun REALLY shone.
RnG is still possible with LMGs, you just need very good anticipation and keep an eye on your clip. Overkill + Fast Hands would benefit this playstyle as you can have an emergency fallback weapon should you get caught short.
Only thing I was disappointed about was that the wildcards counted towards the 10. I thought the 10 only counted weapons/attachments/perks/lethal/tactical selections. Though I understand why they do so I got over it.