Griffins. They are incredibly common and versatile, and many players love them and use them to often. Disliking them means that you are a minority usually (e.g HDIOS) and are a subject to criticism.
The main issue with the Griffin is its health. 158,000 health is completely inadequate for a heavy robot, even with the Jump ability. The Rhino and Lancelot both have more than 170,000 health each, as well as physical shielding. They also have equal if not more firepower than the Griffin, and are equally versatile. Even the GI Patton has more health than the Grffin. Being a heavy robot, it also has quite a large frame, making itself an easy target for most players, especially considering its low health.
What's more, shotgun/machine-gun weapons such as the Thunder, Punisher and Molot T with bullet spread will significantly damage the Griffin at longer ranges where their effectiveness is usually severely reduced, making them useless except for damaging Anciles. But with the Griffin, even a Thunder shooting at around 400m can be a threat to this robot.
Secondly, the Griffin simply doesn't have any outstanding qualities except its jump ability. Sure, you can get to places faster and reach inaccessible positions that have a good view and range but...Haechis, Bulgasaris and Kumihos can dash, Lancelot and Carnage can Rush, and the Rhino can use Assault Mode. These robots all have a 'speed boost' as well except that they move along the ground. Sometimes this is a blessing in disguise. While jumping grants you some protection against rockets (which will usually miss in the air), but it also exposes the robot to sniper fire.
In my experience (as an ex-Griffin pilot and watching teammates and enemies), many Griffin pilots have jumped to cap beacons or to escape engagements by jumping behind a wall only to be taken out or damaged by an alert sniper armed with Trebuchets. Even if the Griffin pilot survives, the significant loss of health excarberates the existing problem of the Griffin having mediocre armour. Seemingly inaccessible places can also be reached by the Raijin, which can climb places even the Griffin can't reach. The cover provided on the ground can be an advantage.
Finally, the Griffin is just...average. It has the same firepower as the Rhino, Fujin, Haechi and Bulgasari, and has less than most heavy robots, such as the Lancelot. The almost unique problem of the Griffin is that it lies in no man's land, like the Haechi. It has too little health to be a heavy robot (but enough to be a medium), but has too much firepower to be a medium robot. It's four weapon slots may seem like an advantage, but its firepower isn't anything special and eventually upgrading 4 slots becomes tedious and expensive to most pilots, taking up time that could be better spent.
Even when marked up at level 12 mk2 the Griffin's health is outclassed by the Golem and the Vityaz (at the same level), bot of which are medium robots. Most medium robots, such as the Golem, Vityaz, Boa and Patton all have much more health than the Griffin. The Fujin, Carnage and Haechi make up for their low health with relatively durable in-built energy shields and have more firepower.
Overall, the Griffin either needs a buff to be considered a heavy robot in terms of stats, at least a health buff of around 10%. Its mediocre health is its main weakness that is easily exploited, even when considering its Jump ability and it being a versatile robot, performing well in many roles. To make the most of this robot, players should use it as a mid-ranger (RDB) or as an ambusher (Stuka/DB) where it can make the most of its decent firepower and Jump ability. Due to its low health, the Griffin should not be used for brawling or sustained combat unless at mid-long range.