The question you have to ask is: Did they need air cover?
I suspect at the moment the answer is no, it is purely a ground threat; is any armour involved? I'd say probably not. The main threat is Small arms and potentially some vehicle mounted heavy weapons. Do you need a 4.5" gun to deal with that? No. Do you need Harpoon missiles to deal with that? Again no. The other question is collateral damage, what exactly is a Tornado/Typhoon going to do when faced with lots of people with AK47s storming the dockside? I don't think they're going to drop a bomb on it. All RN Vessels practice NEO during their workups and they have lots of tactics to defeat the bad guys, the safest of which is to just untie the ship and move away from the dock edge. In that scenario it would be easier to put a slightly smaller yet more manoeuvrable vessel that can easily navigate potentially dangerous waterways.
In any event, GPMGs, Miniguns and a 20mm would be able to keep he dockside well under control until all essential passengers were onboard, the shore party would be able to give plenty of notice of any incoming threats from ground personnel. The only thing air cover would provide would be eyes in the sky and it would be quite difficult working out the difference between bad and good.