How to pilot a PDB and RDB Griff??

lol, don't play the Griffin like a Leo! :-)

Use the jump to...

1: jump straight up from behind cover and unload
2: rapidly close distance on someone you can finish off
3: get away after unloading

A Griffin has a lot of firepower, but not when dead. :-)

It feels squishy because it really is, especially at level 6, but there are some things you can do to preserve Griffin's durability and maximize your damage:

1º - Let your team agro for you, then you go for the enemies. On Shenzen for example, let your team go for the mid beacon first, and when the enemy team starts shooting at your alies, you can ambush them.

2º - Pick your targets wisely. Do not engage one on one against Lancelots with Tarans, Galahads with Plasma and so on. PDB Griffin is a direct counter to DB Griffin, so they should be easy for you to kill if you manage to jump well.

3º - Dont use your jump just to get somewhere faster, you can wait for an DB Griffin to start unloading, take some hits to make them think you dont have the jump, and THEN you jump away. An experienced DB Griffin will not unload at you completely to see if you have the jump first, so taking some rockets will make them think you are defenseless.

Talking about the RDB, he is a midranger, so there is not much you can do mechanically speaking, since midrangers just stay in the back doing their work.
Just stay aware of enemies that may have longer ranges than you, and do not expose yourself too much by overextending from your max range.