I'm curious how common resurrection is assumed to be. Out of every N deaths, how often can characters expect to be raised? Does it vary for you by tier?
Extremely, extremely rare. In 35+ years, I'm thinking it's happened less than 5 times. But it's always dependent upon the story. The possibility exists, but there's always a cost to go with it. This includes things like
revivify and
raise dead.
How hard it is to die depends on the players and the type of campaign. If they are the type of players that like a more scripted epic-style campaign where I'm providing more of the story for them to experience, then it's the 5e death and dying rules, with minor modifications (1 level of exhaustion, + 1 per failed death save - although you recover all levels of exhaustion during a long rest).
In my regular campaign, it requires a 13 for a successful death save. And intelligent enemies will take a final shot if the circumstances warrant it.
In all cases, healing magic is less potent, and requires much higher level magic to heal things like injuries and disease, which cause long term exhaustion.
But, combat is also not the default option to my players in encounters. There are still plenty of combats, but they are careful about when and how they get into combat when they can be, and they aren't afraid to flee.
