It’s no doubt undertiered. But this is a useless discussions. Thre are so many aircraft which are under- or overtiered. But the problem is that Gaijin no longer changes SB battle ratings during the normal battle rating change intervals. The have not done so in ages and the last time they did was during the unscheduled change when they decided that hight tier aircraft have their battle ratings decided solely based on their armament sometime early last year.
There should be discussion as long as this on why they are no longer being adjusted.
What a lot of people forget about is that SIM whoever can dictate engagement wins.
Vixen excels at that just because first of all it have Radar with IFF. That alone in Sim at BR where most planes do not have radars or RWR is huge advantage.
Speed is other thing. Playing when 8.3 is top BR is just like clamping your balls. Sure you can do it but it wont be fun. No nation except US F3D, France early Voutour and Israel Meteor have similar abilities.
Which means all nations relly only on Eyeball Mk.I to spot.
Good luck defending against Vixen who finds you on radar, dips below your nose and fires missile from below your tail.