Agree completely. Sure, speed is one way to add challenge, but like you said.. I just prefer it to be more difficult.
Heroic dungeons = LFR
Challenge mode = Raiding
It should require planning, teamwork, CC and doing mechanisms correctly.
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They are heirlooms for the NEXT expansion.. not for old content. They will scale up to level 100.
Basically you will get your heirloom, but continue using your heroic SoO weapon this expansion.. Next expansion, maybe level 91 or 92, your heirloom weapon will be an upgrade over your SoO weapon and then you can use that heirloom all the way to 100. ( since the heirlooms scale to 100, it is a good bet the next expansion will take us to 100)