Yeah, why is Daybreak a tier 1 super? It doesn't do nearly enough damage, it's damage against bosses with Dawn Chorus got gutted in 3.0, and you don't even get an increased recharge rate of Phoenix Dive with it, futher making that ability useless as well.
Because Bungie stupidly decided to base the Super tiers on their PvP effectiveness. That's why the roaming Supers, and those that have a long duration and range, like Chaos Reach, have a longer cooldown than the one-off, stationary, and slow moving Supers. Unfortunately, their PvE effectiveness was not even considered, so they hardly got any PvE buffs to compensate their longer cooldowns.