
It is soooo easy. But it entirely depends on the style you play. Gritty realism is the key.
And combat rounds are often going into the 7th or 8th round. Our absolute longest fight lasted 25 rounds against a single dragon.
But campaign style and rules are what gives
many short rests character their chances as the daily resource type characters must be careful with their resources. We often see characters taking the dodge action to mitigate damage since resting do not restore HP and long rest is quite hard to get. Feats such as Healer, Inspiring leader, Heavy armor master and shield master for fighters are quite a must. Heck, war caster is the first pick of any casters with spell sniper a close second. Tough is also taken quite often to add a bit more HP.
It maybe why feats such as heavy weapon master and sharp shooter are not problematic in my games. Since HP is a resource to be closely watched, defensive feats are easily seen as very good. A simple heavy armor master, assuming being ht every single round could save almost 21 points of damage per combat. And since we roll damage, sometimes the feat negates damage entirely. An arrow doing 3 pts of damage effectively do nothing to such a character. Les HP loss means less spells spent on healing and more spell spared.
If the characters see that their foes have trouble to hit them, they will go all in after a few rounds but they fight defensively quite a lot. I should try to note a typical fight and write it down as an example of how it is going on in my games.