You should probably not be so hasty in your anger. The haste cap is not "bullshit", it's just a number showing where you get an extra tick of renew. I don't think anyone is claiming that renew is the end all be all spell, but it's still something that occasionally get used so it's a good idea to know when you get that extra tick.
12.5% haste raidbuff - is a bullshit from "theorycrafters" who use Renew and want 5th tick. NO MORE.
It is the rarest spell in holy rotation. It is slow, low heal. It is much faster to throw heal, or gheal and dont waste gcd for renew.
So I agree with poster above. Haste and mastery need to be balanced and they compete with each other in various fight.
And haste "cap" doesnt exists in my opinion. Its always good to throw heals faster. Always.