So sounds like it is more likely a loss of exp from the 'rounding' issues when clicking tablets? That's good, then - exp from killing Alarans may (or may not) be affected, but good that the tablets apparently have not been nerfed as was feared.
Aye, I attribute it entirely to a rounding error, since it was happening when VoA was the current expansion as well. I was concerned at first, as well, with the reduction in XP for RoF and older content, but I no longer worry. Since I've now clicked 5 tablets, and gained 25% into my evolution at level 18.