Use of the ATM from here is certainly not going to cause “massive” dilution. Even if the entire remaining portion of the new ATM (~$68M) were sold in the near future, it would add only 3.5M-4M shares, which is about 5% of the current fully-diluted share count (#msg-113313190).
Whether it's the first ATM, the 2nd ATM, the new proposed employee program or this new stock sale the dilution looks like it'll amount to 50% over a few years.