Not always the case.... I've run the game on the same exact system... other than changing hard drives... and I can tell you... SSD isn't the miracle cure....
With something as multifaceted as an MMORPG... there are tons of places along the way that could serve as a bottleneck....
On a core 2 duo with an 8800gtx... You could have the fastest OCZ PCIe SLC SSD on the market and not run the game properly....
BUT...
If you had an I7 990x and a Radeon HD 6970 and a regular 7200rpm HDD... you'd run the game more than adequately on very high settings....
What does that tell us?
Storage medium is the least of your worries....
Even the networking adapter, ISP and bandwidth make more of a difference than HDD
How can you just diagnose that he needs an SSD without asking what type of Internet connection he is using...
Is it wireless?
Do you share internet with others?
Is someone that you share internet with downloading a lot?
Are YOU downloading a lot?
Is there ANYTHING on your computer, running in the background that may be connecting to the internet, or heavily taxing your hard drive?
What kind of hard drive do you have now?
Do you know the RPM and cache size of it?
Is it more than half full?
I can guarantee you, that:
1. A Western Digital caviar black SATAIII 7200RPM 64MB cache
2. A western Digital Velociraptor SATAIII 10000RPM 32MB cache
and 3. OCZ Vertex 3 SATAIII MLC
You wont notice a performance increase with any of these (Provided the HDD's aren't full)
Now if you have an old 5400rpm 8mb cache drive from 2002... or an eco friendly green drive (FV#K THE PLANET).... then go to an SSD... then yea.. it will look like the SSD works miracles... but going from that old drive to a modern high performance HDD will also solve the problem
Seriously... you can run the game with high end everything else, but a mid range HDD and get no problems at all.... no stuttering... no performance decrease...
and if you are using an old outdated HDD... you're better off getting a TB or higher Caviar Black drive and spending a lot less for a lot more HDD space