Horn of renew, upgrade "protective shield"

Don't know if it's bug, but with %haste effects it working weird... because that upgrade has cooldown 15sec for allies but not for horn of renew user...
Example (even in pvp with only 25% haste):
Warrior getting proc of skull dozer axe, using charged horn of renew (with cooldown 11,25 sec), everyone around getting protective shield (immortality for 3sec)
If SAME warrior will use charged horn again (immideately when his horn ready) - nobody of his allies will get protective shield (only warrior who used horn will get shield)
Looks like that upgrade "protective shield" has cooldown 15 sec for allies... (same way as nekro and glow aa)
It's ok that we can't get much immortality like 2-3 warriors will heal everyone one by one and give immortality for 6-9sec
But I consider it as bug that just 1 warrior can't protect his allies properly because of his haste and imo this cd of upgrade "protective shield" should be reduced to 11-12 sec in pvp and 7-8 sec in pve (not cooldown of horn of renew).