This issue has been around since U13 hit Bullroarer. I /bugged it back then, repeatedly, through every round of the beta (and in the U13.1 beat as well). There never was any reaction on Turbine's part. While this does not hurt me personally (I'm a slow-leveller and use the XP disabler on all my non-grinder characters), I strongly dislike how an aspect of a cash-only item got changed after the purchase, especially since that very aspect seems to have convinced a sizeable number of people to buy the Premium Edition rather than the Base Edition (or not pre-ordering at all), and Turbine never even lost a word about it. The way this played out, it smells of switch-and-bait.
Also, I don't see the reason for this particular change. With the sheer amount of XP our characters earn nowaddays, plus the rather frequent Welcome back Weekends, plus free XP boosts from Hobbit gifts and Store samples, I don't think an additional +25% XP from defeating mobs and crafting would have been game-breaking. It doesn't even seem significant enough for me that it could possibly have cut back on sales of the Gift of the Valar.
It also isn't that Turbine is unaware of the issue. At the start of the U13 beta, the Shield of the Hammerhand was set up in such a way that XP-disabled characters would not get the IXP and Steed XP bonus from it either (that's why I became of aware there was something odd going on). After a bit of noise on the beta forums and several bug reports, the Shield was changed so that the IXP and SXP boni could apply at the same time as the Halted Experience buff. Somebody did something to correct the state of the Shield of the Hammerhand, but they did not completely revert it to how it was before U13.
By all means, keep /bugging this. Keep making forum posts about this. While I'm currently not affected by this issue, I still think it is not fair towards fast-levellers who spent cash for the particular effects of the pre-U13 Shield. I'd also like to see at least some kind of statement from Turbine about this. Their not even acknowledging the change smells of somebody hoping nobody will notice and they can just get away with it.
German, female, migrated from CodeMasters in 2011, Premium member, slow-leveller, pure PvEer and opposed to Forced Emotes - wherever I fit into the statistic, it's not in its middle.