Not every tank should be JUDGED on the same aspects, thats what most players lack awareness in top tier, some are extremely mobile, others pack a good punch, some can do it all without being particular best in any.
The M1 Abrams and the Leo 2A4 have insane mobility in both forward and reversal which makes them a very solid MBT for their BR. Its not about their gun penetration but how you use the mobility to your advantage to secure forwarded positions and tear down enemy teams, secure a good position and your gun will do the rest.
Challengers do not have good mobility compared to other MBT’s at 10.3 or 10.7, therefore they are not tanks to secure forwarded positions but instead play the support role and snipe enemies from afar. If a Challenger player somehow decides to go forward and play out of cover which is entirely possible they’re not using their tank strengths for their advantage rather instead their insticts and skills as a player.
The FV4030/3 is no exception to this, while it sits at 9.7 with a SOLID ROUND for its BR it is in no way in need of a NERF to a higher battle rating. As it is it can get to see the 10.7’s anyway if unlucky to a full up tier. PLUS as I’ve said before the UK doesn’t really have a SOLID lineup to go with it anyway, all backups are 9.3 vehicles besides the one premium Roolkat at 9.7.