BLM aren't necessarily bad for this fight, but they aren't optimal. I don't think it's necessarily fair to compare yourself to a SMN on this fight because we reign supreme on fights that require a lot of dodging and damaging 'off' targets (don't forget our dots keep ticking even when we have to kill jails, jailers, or superbomb). We can spread dots and keep them going while our pet CONTINUALLY does damage, no matter if you personally have to dodge or not. I prefer to only take one BLM to this fight because I know they will have trouble in certain spots, such as pumping out the dps on jails reliably every time -- especially the 2nd one that you are knocked back into and have a few seconds to destroy post-landslide.
If you really want to be doing more damage in the fight... try a different class. I would suggest leveling and gearing up your summoner since you likely already have very good gear for it (if you got a hold of any i90 Allagan or off pieces for your BLM). Otherwise, your damage is passable... but it just won't get much higher in this fight. For the record, there are a few fights I personally believe would be better suited for a BLM than SMN (Ifrit extreme comes to mind, because of all those nails you have to kill)... but that is the nature of this game -- some fights are easier for certain classes than others.
That's exactly why I disagree with people posting parse results. I won't parse anyone, nor have I ever used the program. I know if I'm playing right and I can observe others and see if they are playing wrong. Parsing pushes people to get the highest numbers... and when people do that, they get sloppy. One example I recall is a Twintania run when our dragoon got his parser working and decided to start telling everyone their numbers in the MIDDLE of the fight. There was a marked difference in concentration as people popped their cooldowns in the wrong places to try to 'top the meters'. Meanwhile, I continued as normal, content to save my festers for the best times. I didn't have the highest DPS, but I will say this... every time I was caught in a 'short' conflag after that, I died (although they had previously been breaking me out). People weren't saving their cooldowns and it was painfully obvious and frustrating. I eventually just told the dragoon to stop.