I pointed it countless times already: some of these barrels are approaching the cubic meter in volume. One cubic meter of water would be a literal TON.
Let's say these barrels are half that volume at best and let's concede that OIL is marginally lighter than water. You'd still need an ogre strength to MOVE these barrels around without any mechanical help, let alone to toss them around like bowling balls.
"Realism at all costs" may not be the most important thing in a game, but here we have case where being a bit more realistic would actually implicitly fix a broadly criticized game exploit.
Basically: if Larian really wants to have its exploding barrels laying around, they could at least make it so that they are, for all intents and purposes, just a fixed part of the scenario that the player can't carry in droves, accumulate in specific spot and toss around like marbles.
And IF you have a character that is actually above the strength threshold expected to move a barrel (let's say 19 or 20) he should at most be able to hug one, raise it from the floor and VERLY slowly move it around a bit, let's say like it happens in
Shogun: Shadow Tactics when you move a container.
EDIT: found a Youtube clip as reference:
https://youtu.be/ypgl6cxxIXg?t=544
