I tested this watching my troop losses as I hit strong EBs. Both attack percentage bonus (from equipment) and clan attack percentage bonus apply directly to your raw attack stats, which are based on the number of troops you have. Anyone who tells you otherwise is categorically, undeniably wrong.
Greatness makes a great point. Unload on an eb with the sword equipped and record your troop losses. Once you are fully regen'ed, unequip the sword and unload, once again recording your troop losses. See if your losses match or not.
There has been a thread on this before, devs have replied that the % based weapons are based on your troop levels, so as you dump troops the equipment weakens. Definately not good equipment to use in wars where you are hitting from pin alot, static drops are much better for this.
*Except it has to be an eb where your troop losses increase as you unload without the sword equipped. If you have no weapon equipped and your troop losses don't change then you need to test on a harder eb.
As mentioned by many... % equip is completely dependent on Troop and spy levels. This was settled a long time ago, soon after the 1st 3 EB items were released. Anyone saying they "tested" it and found otherwise have no clue how to test.