Hello,
It sounds like you are putting together a good functional program, and adding E-Stim is always a good idea for muscle recruitment. However, you are missing the reason the foot drop is there in the first place; the disc herniation. We as physiotherapists need to address the root causes of functional impairments to fully help our patients.

I have seen foot drop disappear after one treatment with the following techniques.

The disc herniation needs to be addressed. This can be done by adjusting the lumbar, sacral and pelvic biomechanics with simple muscle energy techniques. Remember that intradiscal pressure increases greatly when the spine is flexed, rotated and sidebent; so is the case when one particular vertebrae is stuck in this way. So, lets take the L5S1 disc for example. Typically, L5 will shear anterior over the sacrum or be stuck in flexion, either way this will bias the L5 disc posterior, irritating the S1 nerve root. We must also remember laws of spinal mechanics, which state that the lumbar spine has both Type I and Type II mechanics. Type I mechanics occur when the spine rotates and side bends to opposite sides, as in a scoliotic pattern (typically 3 or more segments). Type II mechanics occur when the spine rotates and side bends to the same side (can be one or multi segmental). So imagine L5 stuck in a Type II dysfunction where L5 is now flexed, rotated and side bent to either the right or left (FRSL or FRSR); this will greatly increase intradiscal pressure and bias the L5 disc posterior and either right or left, irritating the S1 nerve root. The same goes for the remainder of the spine. Address L4 mechanics for improved L5 nerve function, address L3 mechanics for improved L4 and L5 and possibly S1 nerve function. (The above is assuming a posterior lateral herniation) Also requiring adjusting is the sacrum, as a mal-positioned sacrum will cause the remainder of the spine to compensate and contribute to faulty mechanics, disc herniations, nerve root irritation, protective muscle spams, etc.

By addressing the faulty mechanics of the lumbosacral junction you can greatly reduce the disc herniation (if not eliminate it all together) and thereby reduce the irritation of the nerve root causing the foot drop.