Terrible FPS drops only in certain areas. Any valid explanation?

[Traceless]

Okay so, yes, this is mainly just another QQ letter about low FPS, but there's something that's very puzzling to me, I'm demanding (jk, asking politely for) an explanation.

So I don't really have some sick rig (not really too tech savvy but can tell a toaster from a decent-ish pc), it's i5 quad core 2.7 ghz, 16gb RAM, Nvidia GeForce GT 730 (4gb if that matters?) 

 

The issue is, I'm experiencing HUGE fps drop in certain areas, say, unplayable. Some of them were.... Sapphire basin (around waterfalls), Celestial basin during special events, Asura (during Iruga and Volcano & Glacier my fps goes 20, other than that it's 45ish), so wherever there's a lot of water, rain or "glowy" effects or so, there's always an insane fps drop, as I said, from my normal 40ish to 15~20. I normally play with average graphic settings, but I've tried passing through said areas even with "Optimize for low-end PCs" option and it still did not improve the slightest. Anyone might explain why that happens and if there's a possible solution to it? Of course, other than saying "Get an actual PC" because I'm tired of hearing that as I got this one recently and everything runs just perfectly aside from certain BnS thingies. Thanks!

 

EDIT: sorry, misclicked to post halfway!

[Sempra]

GT 730 is NOT for playing. Its a Multimedia card. 

Change this and you be happy. 

 

 

I had a gt730 and have everytime shit fps... Now switched to a 1050ti (main pc) and a 750ti (second pc) and i have all options on 5, except grass settings and the crazy effect for running makes you dizzy. 

 

I capped my game to 60FPS and i get it overall except raid and mushins tower if there too much players. 

( in BT i reduce texture to 3 and shadows to 1 and all its fine)