The problem with HDs is, they're lidded devices with no heat spreaders integrated into them -- and as everyone knows, air is a poor conductor of heat -- so, blowing a little air on them isn't going to do jack squat. You need a hurricane -- either that or spreaders -- or both -- your choice! Otherwise, 'situation normal'...
Define "hurricane." Yes, air is a poor heat conductor. However,
flowing air is pretty good at removing heat from surfaces which radiate heat, assuming there is a temperature differential. Metal (which happens to be what the HDD is encased in) is a pretty good heat conductor (relative to air), and therefore will effectively radiate heat into its environment (air).
I have two 92mm fans spinning at ~1000RPM blowing on my soft mounted WD HDD. The drive is standing vertically such that only one (long) side is facing the air directly.
Room temp = 24-25C
Case temp = 35-36C (air middle of the case, measured via probe)
HDD SMART temp = 33C idle, 36C load
HDD case temp = 36C idle, 39C load (measured with probe)
The drive will quickly reach the mid-40s without any airflow. A drop of 8-10C due to <35CFM of airflow is hardly "jack squat." This situation is hardly special- all of my rigs exhibit a similar behavior, and a search of the forums will show this to be the rule.
55C is not "normal." My best guess would be a faulty sensor- take the advice of the previous poster and do a finger test. Anything above 50C will begin to feel painful.
And, even if your drives were running at 55C, that is still within spec for WD. They will not die within a year due to heat-related issues if this really is the case.