My employees have to remove the lens cover, remove tubes, take off the ballast cover to troubleshoot fluorescent fixtures. What HRC would this be?

What voltage? Is the panel that feeds the lighting circuits fed from a transformer less than 125kVA and the voltage is below 240V?
Have you had a study done of the arc flash hazards in your facility?

Technically there is no applicable HRC. If the task you want to perform is not specifically listed in the NFPA70E tables, you need to perform an analysis.

There are dozens of examples of where employees have been electrocuted while checking ballasts in fluorescent lights so shock protection is critical.

In looking over the years 2007-2011 (most complete, most recent 5 years) of OSHA investigations, there were 9 cases of installing or removing a bolted cover that went badly for arc flash. One involved a pinched wire. One involved a piece of steel that fell into a lighting panel while it was being removed. ALL of the others involved where the electrician lost control over the cover and it came into contact with the energized parts. None of these however involved fluorescent lighting access covers.

Considering that the vast majority of fluorescent lighting is going to be on relatively low power circuits (120/240, 125 kVA or less), it is no wonder that the odds are against an arc flash injury occurring while performing this task. However, I have encountered much larger transformers and much higher voltages with lighting on more than one occasion, including lots of 277 or 480 V HID lighting circuits. So don't assume until you know what your situation entails.

I have done a lot of 277V lighting in an industrial environment as well - both fluorescent and HID.

It's quite possible to be electrocuted without there being an arc flash. The danger in checking or changing the ballast comes from the possibility of touching an energized wire, and having the current cause tissue damage and either stop your heart or cause arrhythmia. The easiest safety measure is to turn off the luminaire before working on it. The procedure is: 1- change the lamps ("tubes"). If the new tubes don't light up, then 2- turn off the luminaire and replace the ballast.

While I don't disagree with the sentiment and the fact is that there are plenty of documented cases of electrocution while doing this exact task, don't forget that now that you have turned off and locked out a switch and are now standing on the ladder again with the lights off, are you SURE that the lamp that wasn't lit before is now dead? How do you know that? Lots of guys that were shocked but not killed from the shock, and died from injuries falling off the ladder thought the same thing...I turned off the switch so it must be dead, and now so am I.

OP needs to consider shock protection to be sure, but also needs to consider arc flash PPE just in case. The fact of the matter is that it is highly unlikely that arc flash PPE is necessary but doesn't make the issue go away.