Whether a person does or does not do high-end content is irrelevant. The only time it should be relevant is when they are speaking directly of that specific content. Classes will only be a matter of understanding them, and not all people who understand the jobs will do that high-end content. Equally, if a person with a poor understanding of healers is able to get by with absolutely no issues whatsoever in the content they are doing then this is a problem.
Regardless of the level, be it normal mode or extreme, savage or ultimate... If an entire role is, or can be rendered moot then it is a problem - Whether the role is a tank, or a healer. All encounters should require a healer, and have some form of mechanic that healers need to engage with.
If I can go into a dungeon right now, and have my entire existence rendered moot by a tank that is busy playing god then that is a problem. E.g., Bloodwhetting not being penalized in AoE situations is a problem. This near enough renders a healer irrelevant on the only threatening part of a dungeon. -- Dungeon bosses do very little damage, and said damage across the party is so sparse that in many cases passive HP regen everyone gets by default covers most of it anyway.
Anyone saying you need to do xyz content before your complaints are valid are just being both dismissive and just doing the most disgusting form of appeal to accomplishment humanly possible, and I certainly hope any people being dismissive over this aren't subsequently getting upset over Yoshida's dismissal of "If you want engaging content, then go play ultimate" - Because they both effectively border on the same limited mentality.
That being said, I don't think a healer strike will accomplish much in any scheme of things.