As a fanatic of every brush, i'd have to say that the octobrush can be anything. It all depend on how you play. For exemple;
I'm a very agressive player. As soon as i see an ennemy, charger or not. I charge in. Not head-on obviously-- Walls are any weapons' best friend.
If i where to use the vanilla octobrush. I'd play patiently. Charge your kraken, place a beacon near ennemy ink and wait for that one player to try and get rid of it ! Then, you simply pop your kraken or simply charge in. You'll have the time to splat them. And if it fail, the kraken is a safe bet to protect yourself and maybe get that precious splat or more.
The octobrush is the kind of weapons that you're more rawarded when you use it in an offensive way. But you can use it for defense just as well ! Kraken could be used to force ennemy away from the objective, beacon to allow quick access to the turf and the octobrush in general can cover ground and push back another kraken very well.
How ever. What i say are mostly opinion based, the only weapon i know for sure is the octobrush nouveau ;v;b