I'm not a pilot, but an engineer for an offshore oil & gas company.
We don't have a 'hot flare' on our installations, but we do have some gas turbine engines that emit hot gas. Every time we modify the installation (by putting in another gas turbine) we have to do a 'Plume Study' which is essentially a computer generated 'wind tunnel test'. The worst case for us is when the wind is 'light' and obviously from a certain direction. In still air conditions the hot plume goes straight up, in strong wind the hot gas is dispersed quickly. In light conditions the hot air can 'waft' over the helideck. The outcome from the plume study is a calculated air temperature rise at the helideck, and our helicopter operator is advised accordingly (and I assume modifies his SOP to accommodate).
I'd normally expect the vent to be in the 'obstacle free sector' of the platform, so given the prevailing wind conditions you'r expect the vent to be in the lee of the helideck.
A platform venting gas during an emergency shutdown is obviously another hazard, and we have a 'Helicopter Wave Off Light' on the helideck to warn the pilots if we're about to vent gas.