What efficient techniques exist for rectifying high voltage?
At 5A power handled = 120 x 5 = = 600 Watt so your 11Watts of dissipation is about 2% loss - this oild be acceptable in most cases. The cost of getting lower losses may exceed the cost of heatsinking 11 Watts and the reliability may be lower.

BUT: Schottky diodes may about halve power losses. High Voltage SiC Schottky are available. Beware of the can-be-horrendous reverse leakage at elevated temperatures. 

As Martin says - synchronous rectification will work BUT the cost of switch devices and controller may be dearer than a heatsink. If eco-greenery insists on low losses then the expensive solution may be needed.  Your 1.1V/2 diodes at %a = equivalent R of R = V/I = 0.55/5 = 0.11 ohms = 110 milliohms.To be useful a synchronous rectifier MOSFET would need to be &lt;&lt; 110 milliohm in a 200 V +++ FET.

Doable, but a heatsink seems attractive.