If you spend 500 hours looking for that one item then you are missing out on the hundreds of other items (rares) that sell for 1 to 100 million. I sell more rares than legs and have made more money doing so in the near 1000 hours I have played. Heck, I have only found one 5.5 CC mempo and that was this weekend after nearly 1000 hours between two characters.
Maybe the bonus EXP won't be very useful to people near 100 paragon, but then again any MF bonus (that doesn't exceed the MF cap) would be redundant as well.
I'm happy with the bonus to XP at least, since now I might actually play MP 4-5 to lvl up all my characters.
The only other thing they could consider imho is a gold bonus. But I doubt they will, since a lot of people say the game's saturated with gold already (aka there's too much gold in the economy) and we need more gold sinks, not more gold
Faster XP also makes leveling alts more appealing, either from 0-60 or from 0-100 paragon, which in turns increases the replayability of the game or extends the lifetime of the game for people. For those of us not leveling very fast on our mains, it also lets us finish the paragon leveling faster.
Actually, the increase in XP seems more like a way to give us better farming options. Currently, just about every XP farming guide says to farm MP0, even with 200k dps (slightly depends on class I suppose, since I'm mostly familiar with a wizard). People don't want to farm MP0 because it's too easy, so they try higher MP which are less efficient, but they dont' like that. Instead, they're raising the XP gains from higher MP to make the XP farming more in line with each other. As was seen from a few other threads with various players competing for how many legendaries they loot, the gain in MF and bonus items from higher MP balances with the higher mob HP so that the approximate legendaries per hour doesn't vary a lot with MP level, at high gear levels. This will make that true for XP, so you can have a lot more freedom to choose your preferred MP level without taking a 50-75% hit to XP per hour.