It's actually your system related to the graphics engine used.
Your system itself is quite old, and although the CPU still has some kick, it's lacking raw video processing power and memory. The GPU is kind of old, as you basicly have one of the former models supporting DX11, while the RAM is outdated, being DDR2 instead of 3 and being 3GB instead of a minimum 4GB (nowadays, if you want to get anything at high details, you need at least a 2/3 GB GPU and between 4 and 6 GB of DDR3 RAM, but if you're not that much interested in details, even 4GB in RAM and 1GB video cards are ok-ish).
This gets mixed up with the engine used by ArcheAge. While GW2 uses an heavily modified version of its previous episode's engine, with the help of Havok and some other friends, ArcheAge uses the CryEngine3, which is the same one behind Crysis series (namely the third episode), It's like comparing a feather to an iron weight...
And there you go, you have your "stutter cocktail" served, ice cold
In any case, a full system upgrade is highly advised, as it'll not be long before those games you play at minimum settings become completely unplayable...