I agree on this; I'm at the same SR and the compositions I see are all over the place. My preference is for 2-2-2 but a single healer or single tank can work. I don't really like 1-4-1 that much. I'm not precious about this but if we're not working, something should change, don't just beat our heads against a wall being countered.
I see a lot of Mercy solo healing, with mixed results. If I end up filling healer I seem to end up solo healer quite often (because I usually start on tank, so if I'm switching off tank we're probably 4 dps) and I just can't solo heal with anyone else.
I see a lot of solo tanking, and if I end up being the solo tank I often feel like I have to run Rein; I'm actually getting better with him as a result.
Despite the focus being on the tank count or healer count, actually it's the dps who are the most relevant. If they're not getting kills we aren't going anywhere useful. Quite tired of instalock dps players who are then ineffective at dps or are one-trick and get countered.
My preferred rules are:
2 tanks for payload push, 1 is too easy to get focused and taken out and then you're trying to hold an area with less robust heroes.
When facing dedicated harassers who are doing a good job of it (Genji/Tracer particularly, and sometimes Sombra) need 2 heals or a properly protective tank or Mei.
If it's working, it's working, I don't care if that means offensive Sym/Widow or Mei icicles are the only counter for but are slaughtering Pharah or our tanks and dps are ignoring harassers but Zenyatta is pro headshotting the enemy Tracer when she tries.
Dedicated counters:
I'll D.Va if they have a Reaper and even then needs dps to actually focus him when he's locked down.
Soldier, McCree or the less preferred Widow/Bastion if they have a Pharah, and I'd prefer to be D.Va to matrix rockets and boost harass her. Winston can be enough if we have good hitscan, his bubble covers them while they pick her off.
If their D.Va is being a solid anchor and it's why we're not doing so well, I'll switch Zarya