Well, it is the 5th edition of D&D rules and the first game i see which has it. None of the prior games were broken. For example, 4th edition bless simply had a duration of 1 minute. On some spells, the concetration mechanic seems appropriate like a detect evil or even the witch bolt, which can be cast each round without spending a spell slot.
Having played through the EA a few times now, in most cases it makes tactics using some spells outright useless. As mentioned, a CON save on most casters has more than 50% chance of failing and that goes up dramatically with higher damage. Most of the time i end up casting magic missles because those cannot fail and do a decent amount of damage (especially with that psycho item, THAT unbalances the spell btw.)
It is just my opinion on this, mostly because it feels awkward. You see, spending my clerics action on a bless only to have it broken in the same round most of the time is hardly worth it. That action is better spent otherwise. I can't even use shield of faith to make the char harder to hit because i cannot bless anymore after that.
From a certain viewpoint it may be interesting to have need of choice of either strenghening your own party or weakening the enemy (Bless or Bane) but as the Mobs succeed in 2 out of 3 saves anyway it goes again to rather take some HP off before trying to weaken them. For me, it takes a lot of fun out of tactical combat.
So many fights failed trying to use buffs and debuffs. in the end i just hit them with damage and won. This definetly needs tweaking and even though i love a bit of logic in fantasy games, sometimes its better to leave it fantastic :P
