leave with exp bonus inaccurate after passing the cap

[Moonwood]

Time: September 16th, 2013 around 3 AM GMT
Frequency: everytime
World name: Coeurl
Character name: Ashitaka Amane
NPC name: N/A
Monster name: N/A
Class/level: botanist 48
Party or solo: Solo
Race: Hyur female
In-game time: unknow
Area and coordinates: Coerthas Central Highland
Steps:
Quest name : Plague on both our forests (lvl40)
At level 48, the quest bonus became impossible to get. You can get 5% exp bonus but not the 10% neither the 25%.
Indeed, the quest is about logging 8 trees. You can log 6 times a tree for which you get 6pt per logging. A total of 36 pt per tree. If you harvest them all you can get 288 maximum.
5% 286 pt / 10 % 303 pt/ 25% 320 pt
How can I get more points when I can only harvest maximum 288pt for a perfect logging?
I tried "blessing harvest II" which allows me to get 3 items in the same row, but of course I get the 3 items but it count still as 6 pt the log.
I tried "Ageless Words" which allow me an extra log per tree, but it's not working.
I had the same issue with the same type of leave with exp bonus "The palm in your hand" if I recall well.
This issue only works when your level is far from the quest level. As the points increases with each level you taking.
If I'm wrong and missed something forgive me.
But I believe the leave system is inaccurate in that case

Connection Specs
Type of internet connection/provider : Broadband / Ethisalat
Modem maker/model number: Aztech / HW550 -3G
PC Specs
-=-=-=-=-=-=- System Information -=-=-=-=-=-=-
SYSTEM_OS Microsoft Windows 7　Ultimate 64bit (6.1 build 7601)
SYSTEM_CPU Intel(R) Core(TM) i7-2600K CPU @ 3.40GhZ 3.70 GHz
SYSTEM_CORE_NUM SYSTEM_CORE_LOGIC 8 SYSTEM_CORE_PHYSICS 4
SYSTEM_BIOS Default System BIOS
SYSTEM_MEMORY 8192 MB
SYSTEM_PAGE_FILE 13901 MB
SYSTEM_STORAGE C:\ SYSTEM_HARDDISK_DRIVE SYSTEM_TOTALDISC_SPACE 167 GB SYSTEM_FREEDISC_SPACE 117 GB
SYSTEM_DIRECTX_VERSION DirectX 11
SYSTEM_GRAPHICS NVIDIA GeForce GTX 560 Ti

[Xetyline]

Greetings Moonwood!

We appreciate you taking the time to report this concern you are having to us. However, since this sounds like gameplay rather than a bug report, I will be closing this particular thread. We welcome you to post about this concern in the "Gameplay" forums in order to discuss changes you would like to done to the game. Thank you!

Regards,
Xetyline