how?

he just derps with Q and hurrfire torch and all my hp is gone even with MR

Rumble already did a ton of damage.
It's just that (almost) nobody played him.

Now that we have Torch, seems more people are playing mages, and thus more of the strong mages are being made known.

1). Pick any champion with ranged abilities.
2). Buy BFT.

Congratulations, you can now deal with BFT Rumble!

Sauron says fo fight fire with fire.

I see what you did there...

This only matters for the relatively small amount of picks between "Rumble melts" and "eats Rumble", and perhaps brings a few more from the latter into the former.

MR still counters BFT as it does to Rumble in general. If that doesn't help, you were probably boned before still.

dont play jax against rumble ._.

What Sauron said. Try BFT Urgot.

Play AD Malz, stomp him into the ground over and over. BFT optional.

Most mages are stacking flat pen which is what is making them do high damage with bft. A simple negaton cloak negates this.