Before I being: Its a very middle of the road feat and you can be disappointed it wasn't jaw dropping.

For this thought experiment, let's assume level 4, 4 person party, where one - two people have trained or higher in medicine

You just got out of a fight. [insert martial here] is badly hurt, [insert martial here] was on the brink of going down, but a timely heal put them fairly close to full, but still down enough where its significant, and you and [insert spell caster here] took some chip damage but are otherwise alright. You need about two successful treat wounds to put the martial that is very down close to full, and you need to refocus as well.

Each time before you do any of these 10 min activities, you take one minute to do sacred ground. Each person in your party gains 4 HP, equalling 16 HP each time. Doing this three times nets the entire party 48 HP. Now, obviously, all of this HP is not being used as characters don't get HP when they are at full. Let's be conservative and say 20 HP of this was used (this is probably a very low estimate considering the situation, but just to prove the point). Beating the expert DC of treat wounds, on average, will get you 18HP, and you have to make a check to beat that.

Without Sacred Ground, this situation can be more tenuous for this party. If there is a time pressure or any other reason why you can't spend an hour or more healing up, then what do you do with everyone? Do you waste time or resources getting the spell casters up to full, or have them walk into the next fight already down on HP? If there is an extreme time pressure or a very immediate threat, what do you do with the martial that is mostly fine?

Again, this is a very middle of the road feat. I don't see it becoming a must pick option and I don't see it become a favorite feat. But, it has a very clear benefit and slots neatly into basically any cleric build.