Eh, they can be useful sometimes, if you have a good balance of them with infantry and keep them well protected, they can be useful for picking off enemy support lines, but the last thing you want to draw when you're being swarmed
I am thinking about making an alternate deck with US/Soviet cards, trading off Britain's defense with the 'drowning in bodies' strategy, I already try to partly do that, plus it would be nice to draw something other than planes in the late half of the match when I barely have anything to defend with
my favouite senario is when I keep drawing "reserves". basically I gain 2 light infantry +1 for each previously played "reserves". So the enemy has to deal with wave after wave. each one bigger than the last. so they wither waste lots of lighter units (most often) or a bigger unit., which
I have one tank card that gives me I think 2 more cards if I have something in the frontline
Bad thing is I only ever find myself drawing it in situations where the enemy has the frontline and am usually forced to take it back using said tank, which defeats the purpose.