Fuck how hard is it to stand behind shielders instead of running round like a retard? You make it sound like we're dealing with nuclear engineering.
Standing behind a shielder is not the problem. But unfortunately melee players have to move to reach their target so they can kill it. Which means you have to move behind a moving shielder, which is a lot more difficult, especially without TS. And a single shielder only covers like 10-20° in front of you, not the whole 180° you'd need most of the time. So you need more shielders than one to be covered properly, and those shielder have to move in formation to not open any gaps where ranged can just shoot between the shielder into the group of shieldless players.
It's not nuclear engineering, I'd rather place it somewhere around the difficulty level of micro engineering.
Edit: does the Roman testudo tell you something? Any formation which is less perfect than this one will only cause more problems instead of helping, as the chances for missing your target are even lower.