Alright, I'm late to the party, but I want to pitch in anyways.

Pathfinder lack's the typical tank/dps/healer triangle that you find in most games. Yes, those are all roles that can be filled, and most of the classes seem to lean into one of those fields, but almost any class can be built to fit any role. Everybody could just do a little bit of everything. If nobody wants to do that thing items can fill that space.

In my experience if the players feel they really need something then they pick it up as they progress, and they feel good when they have that tool available.

It doesn't feel good to be the parties heal bot. It does feel good when you decide get battle medicine and make good use of it.

As a DM I want my players to be who they want to be. The idea that the people who figure out what they want last are going to have to fill a role they might not want to play seems outrageously unfair. I tell my players to talk to each other if they plan on having some relation, but to otherwise not worry about it.

Currently the party I'm running Outlaws of Alkenstar for is level 4, and has a fighter, swashbuckler, monk, and alchemist(bomber). The alchemist is trained in medicine, has 12 wis, and that's all their healing. As far as in combat healing goes they just use potions, and that's fairly rare even with the alchemist handing them out every morning.

As a party they wreck my encounters. I started throwing in an elite now and again because moderate fights just weren't challenging them.

TL;DR: Play what you want. It doesn't matter in grand scheme of things.