https://forum-en.gw2archive.eu/forum/info/updates/Game-Update-Notes-November-26-2013/first#post3264349
Read the section on “Improvements to Agony Resistance/Infused Gear”.
In particular:
Newly created or dropped infused ascended equipment will have empty Agony Resistance slots.
That slot has replaced the inherent +5 AR. So yes, now it takes extra effort to get the additional AR.