This is very good judgement on your part. For your machine (not talking of the others that've posted) it can't be the recent patches, as these patches do not impact the old benchmark tool nor Metro.
While true what you prior said (that it's probably something with your installation)... I personally wouldn't reinstall the OS just yet, and would continue looking for the cause. Reinstalling isn't guaranteed to make the game work better either and may just take up more of your time / leave you with the same results that you're getting right now.so should I reinstalll W7 or not? I'm not sure what to do..
Check power-management:
Unlikely to make as much an impact as you're seeing, yet the usual default power profile for any new install of Windows is "balanced". Try selecting the "high performance" plan.
You can change the active power plan from:
-start > control panel > power options
OR, if the above settings were 'locked' by the person who installed Windows.
-start > run > gpedit.msc, Computer Configuration > Administrative Templates > System > Power Management > Select an active plan.
Check memory configuration:
-You mentioned not having all 6GB of your ram recognized on receiving the machine back. Additionally that someone touched your machine and did a "full rebuild". Make sure that your DIMMs are inserted in a proper configuration for Dual Channel operation, and verify the memory controller is indeed in Dual Channel mode (consult CPU-Z and the manual as mentioned before).
Single to Dual Channel mode can make a significant performance difference in games. Dual to Triple channel, not so much (already sufficient bandwidth).
Double check the version of your PCI-E controller drivers installed (make sure that the chipset installer updated correctly):
-Open the Windows Device manager.
Start > Control Panel > System > select "device manager" from the left tab.
-Scroll down and expand "System Devices".
-Look for *** PCI Express Root Port *** (*'s indicating wildcard / fill in the blank here)
-Right click on the above found item, select properties.
-Select the "Driver" tab.
-Look at the "Driver Date" and "Driver Version" field.
Is the driver date xx/xx/2006? If the drivers listed are 2006, then the Intel Chipset installer did not correctly update drivers.
When all else fails:
-Uninstall your current video drivers (using the control panel option, and then using device manager with the "remove driver" checkbox checked)
-Repeat until you only have a "Standard VGA" display adapter installed
-Reboot in safe mode.
-Clean old driver entries completely off the machine. (Eg, using DriverCleaner.NET, Driver Sweeper, etc etc, or one of the many available online "manual" deep cleaning guides)
-Reboot back to "normal" Windows (not safe mode)
-Reinstall latest display drivers.
-Recheck performance (of both FFXIV:ARR and Metro LL [your other installed game]).
If performance is still low, repeat the above and rollback to 'older' drivers. (perhaps the new drivers do not behave well with your hardware and the games you're playing)
Ask yourself: Is it possible that the drivers your prior Windows install had weren't updated? Newest does not always imply best, even if it often does.
Other thoughts:
http://support.microsoft.com/kb/2670838
Check if your machine has the latest DirectX platform update installed. If you had Internet Explorer 10 or later installed on the machine, then you'd have this by default.
Sometimes people using their own browsers, like Firefox, Chrome, and so on don't install IE10, and thus don't automatically get this update. This is known in rare cases to cause problems with AMD cards, or to fix problems with newer AMD drivers that addressed the issues that started after the platform update's release (eg, the fixes from AMD in their drivers caused new issues without the platform update installed).
EDIT: (more)
The technician who reinstalled Windows on the machine likely did NOT do an install using the default Windows disk (too time consuming to be worth their time), yet rather used a specially created install media or "cloned" an already configured image to the computer and then performed a peer2peer adjust [*cut the total install and update time down to 20 minutes or less*].
In any event ... it's hard to know how this image has been adjusted, such as if common drivers have been installed and updated on the base image multiple times, or if errors have been introduced from repeated slipstreaming of updates to keep their media 'up to date'. "fresh" in an install put on other than by yourself is, well, probably a different meaning of the word fresh.
--Fresh to a technician could be a base image that they've been modifying in a virtual machine for 'years'.