Another grappling-focused aberration? They must have been on discount.
Let's start with the base chassis. Cloakers are large with good stats all around, varying from 14-15 (the mental stats) to 21 (strength). They also have a fly speed, natural armor, and two weak natural attacks. Their bite attack doesn't have reach, but their other attacks do, including mouthpick weapons.
All this is before their special attacks, of course. Firstly, cloakers can engulf foes. This is basically a fancy grapple, but with the added benefit of partially transferring attacks against the cloaker to the grappled creature. With the way combat works for on the player side of the screen, I doubt it'll see much use, though.
There's also shadow shift. Using it (a standard action) lets the cloaker create concealment, mirror images, or a silent image. These abilities will probably be used out of combat, or as pre-battle buffs.
Finally, cloakers can moan. This infrasonic attack can inflict several strong status conditions, such as panicked, paralyzed, or nauseated and prone. That's effectively a battlefield-wide SoL.
Are there no downsides at all to cloakers? Well, the six aberration HD are obviously not great. There's also the issue of advancement: spellcasting is crippled by the RHD and your main ability can't really be advanced in any way.
With all that taken into account, I consider a LA of +2 more than appropriate. Cloakers have a strong chassis with stronger abilities. The RHD and lack of advancement is annoying, but acceptable.