A 4.3 billion USD valuation at exit is not all bad news I'd say. Better a deal at 4.3 billion than none at 5.5. I'd be laughing all the way to the bank with an exit like that and not worry too much about what could have been.
If this was a private company/startup, of course you'd be laughing all the way to the bank. Not so if you were a public investor in LogMeIn. Far from it.
So the consensus is what it is given normal volume, likely a relatively small chunk of shares changing hands repeatedly rather than a really large block being sold once. The latter would almost certainly depress the price.