Defense against a deceptive lease

My siblings and I inherited mineral rights for land in Martin County. In February 2016 we received a letter offering to lease our mineral interests which appeared to be under legitimate terms and from a legitimate company. We had a paralegal review the lease and she thought it was a standard lease, so we accepted the offer and signed a lease with the group in February 2016. In January of 2017 we were contacted by a Dallas law firm indicating that the lease we signed was not a straight forward lease but rather a document essentially buying our interests and that the lessee now “owned” 75% of our total interests. The law firm was preparing to file suits against the group on several other’s behalf on a contingency fee basis and gave us the opportunity to join in. We engaged the law firm and nothing has been filed to date on our behalf. Recently a class action suit was filed against the group who was writing the leases. Has anyone encountered a similar situation or know of one? We are trying to decide if we should stay with the Dallas firm, join in the class action suit or try and negotiate directly with the individuals.