I've got 2 70 with their epics and a 68 that will probably have her epic when she hits 70. They do make things faster and easier. I do just fine in instances and in some cases even top the charts.
However I've done both. On my Spriest I got her FSW and spellstrike sets before her epic. I think the trick is to find a good medium. A lot of people hit gear hard and a big part of that is gems and enchants. People will easily spend 100's of gold for blue gems instead of the slightly lower green ones at a fraction of the price. I'll take 2 less sta or 2 less spell dmg for a ton less gold and use what I save to fund my epic flyer.