Yes, in 3e clerics where far better than any non cleric at soakimg damage. There wasn't much point in playing a fighter, because clerics
I have more slightly experience than you (IRL Weekly game + another game on occasions). Though, I almost never see someone pick both. They pick one or the other and build their playstyle around it. Is picking both something that you come across often?
Anyway, the point is Cure Wounds doesn't have to be as strong as Healing Word, or vise versa. And more importantly, trying to nerf Healing Word isn't really going to cure whack-a-mole, because whack-a-mole would still exist without it.
My group had this problem in 4e once. It was because the Defender was doing their job too well, they managed to set up a chokepoint and all of the damage was focused on just them. It wasn't even a particularly hard encounter otherwise, 4e was just not set up for one person to take all the hits.
Yes, HP (and healing surges) is a resource that every character has in 4e (and in most versions of D&D).
Focus fire, even on a poor target, is usually an optimal tactic. "forcing" your DM to focus fire on one PC is usually a bad plan.
This isn't true, of course, in any game where the defender can survive a round of full focus fire, and healing them to full is trivially cheap. I played everquest, and the spell "complete heal" was a high efficiency 10 second casting time (plus 2 second cooldown) spell that healed for basically all of someone's HP. It was intended as a non-combat spell.
In devolved down to making a fighter type that was as least likely to die to a single round of a monster's damage, then having a coordinated cycle of clerics all casting "complete heal" at a frequency faster than the monster's attacks would land, so the fighter type would be at full health on every attack round of the monster.
You'd have backup "sacrificial" tanks whose job was to take an average of 1.5 rounds of damage (and die) if the main tank died, and a secondary tank whose job was to wait for the "sacrificial" tanks to buy time as the healing cycle would transfer over to the secondary tank. Then the secondary tank would lock down the monster.
It was a game whose mechanics was based off of D&D (well, Dikumud, which comes from D&D), and the only job the "tank" warrior type had was to (a) convince monsters to attack them, and (b) be a slightly more efficient way to convert the healer's ability to heal into negating damage.
I get that D&D isn't that, but every time I see "healers should be able to heal for a long time and while not out of resources, it should be nearly impossible for the character they are healing to die" I think of it.
I personally think that adding durability to a party should consist of mainly adding a durable PC, not a healer.