If you play a villain correctly there is a lot of tension.

A villain using his multi-attack on the same PC. PC goes down with the first attack and then Villian strikes the PC for the second attack causing a double failure on the death save. A villain doesn't always go to the next PC to attack. Remember it is a 6-sec decision.

Then the live PC have to scurry about trying to save their party member.

A spellcaster cast magic missile at a PC, the first magic missile causes the PC to go to zero, and the other two missiles hit him. Because of the extra attacks of the magic missiles, the PC by rules as written is dead.