No, it can be very OP with the proper builds.
Op stated 15 hp extra at level 1. Thats more then most if not all classes get at level 1. When they add barbarian, that extra 15 turns into 30 when they rage. How so because unless your casting spells it's only taking half damage. Same if you cast bladeward on the warlock with 15 extra hp, and with armor of Agathys he's getting hit taking half damage, and dealing damage. Then there are ways to build any character really. That just continues to increase that seeming tiny 15 extra hit points. Potions of resistance which do stack being another way to further turn that 15 into 30, then items that if you fail under x number of hp you heal on hit xdx. You now have someone who has 3x the number of hp as anyone else (maybe even bosses) is healing themselves on attacks, and bonus attacks, plus getting healed by cleric. Can very well with another potion get 2 attacks, or 3, or 4 per round.
With the number of booms, everyone having surface things, barrels, yada, yada it is thought provoking, but still no. maybe on another game not based on 5e. Or if they keep everyone having spells, areas of surface creating, hundreds of barrels per square inch. then I may change my mind.
