Are Large Blisters Common After Laser Therapy?

The legs heal very slowly.  That is a long time to be healing, though.  If you had a ruby laser, I would expect a week or so of your legs looking bad.  But for most lasers, you should be healed. I would have to know your  laser and therapy for an accurate answer.  I would also not rule out that you are having a reaction to the Neosporin and inflamed from the medication.  I would switch to Aquaphor.  Be sure to talk with your doctor about this first.

If appropriate precaution is taken (e.g. perform test area, icing if chilled tip not availabl) , there should not be any blistering or scabbing after laser hair removal. When blistering or scabbing occurs, you should demand to be evaluated  by the supervising physician, start lubricating the open sores and possibly start oral antibiotics to prevent secondary infection. This is illustrative of the need to ascertain the supervising physician of a laser clinic be a board-certified dermatologist or plastic surgeon who is competent to manage post laser complications such as blistering and/or post-treatment pigmentation.

A CO2 laser creates a second degree burn of the face and creates an open wound or blister. The healing process will lead in selected patients to an aesthetically improved appearance. There are negative consequences as well.

Laser vaporizes tissue then relies on the body to heal and repair the tissue with scarring and some regeneration.
Fat grafting does not destroy any tissue and the stem cells in the fat actually rebuild and restore your skin.
The video below explains some of this and shows what can be achieved with fat grafting. I gave up laser some time ago precisely because of cases like yours.

Your experience is not normal. Blisters are not a desired clinical endpoint for any of the laser treatments we provide and we have done 75,000 of them over the past 5 years with 10 different lasers. If your legs were being treated it's possible you were getting hair removal, spider veins or even brown spots. None of these conditions would normally result in the kind of trauma and infection you are describing.
What is just as concerning is the cavalier attitude of the "technician" you describe. Class IV medical lasers are legally only for use by physicians, nurses, nurse practitioners and physician assistants in the state of California. Did the "technician" that performed the treatment have one of those licenses? If not, you should be considering legal action, given the nature of your condition and the attitude of the person that saw you.

Large blisters after laser therapy is not the norm but can happen as a side effect.  Assuming the treatment on the legs was for hair removal, blisters can develop if the treatment was particularly strong or the skin became tanned between treatments.  The problem with lower extremity blisters is the prolonged healing time.   It is not unusual for the process to take close to a month; however, I would recommend another follow up with the physician vs. the laser tech and to change topical agents to aquaphor instead of neosporin.

It is not normal to have blisters after laser treatment.  What treatment did you have and which laser was performed? Did a physician treat you? I am so sorry you had this side effect and blisters tell me too much heat was used.  Please find a board certified dermatologist to have the best results.

Blisters can be a concern after a laser procedure, especially if they have not healied after a few weeks.  I would suggest contacting the physician involved with this laser treatment and have the physician make recommendations as to management of your healing skin.

If blisters appeared immediately after the procedure, most likely it was a burn that caused them.  Blisters are not a normal result of laser treatment.

If you are not getting any responses from the doctor under whose supervision the laser procedure was performed, I recommend you see another dermatologist for an evaluation as soon as possible.  You do need to know what type of laser and what settings were used during the treatment.

Also, if you call the office where the procedure was done, speak to the patient coordinator or office manager and explain the situation, the office should make accommodations to see you right away.

Burns can get infected with bacteria or viruses and may scar worse if the infection is not treated.

I hope that you are not talking about blisters on your legs following laser hair removal?  If so, please see a board certified plastic surgeon immediately.  There should be NO blisters after laser hair removal, only a slight redness around each hair follicle.  This is NOT normal and you should seek care elsewhere.   Burns on the lower extremity can quickly become very serious, and plastic surgeons are expert in burn care.  Do NOT delay.