What I have found is if you are face against something that blocks pathing such as indestructible debris, or for instance the sin heart the middle bear will go straight but the side bears almost take off in a 90 degree angles to the right and left, so I know what you are talking about.
using bears and maximizing their dmg output is to use the environment around you to your advantage. putting your back against path blocking objects not only seems to stream line the bears but also increases their range as well. The odd thing I have found with bears is cast box, It seems to take place behind your character. This also has its uses if you are out int he open and something is approaching you from behind you know you will get some damage onto it. But when you have your back against a path blocking object it seems like the cast box is pushed forward so bears start spawning jsut slightly ahead of you.
I think this was done so if you where up against a wall you dont see zombie bears acting like ghost bears and passing through walls
As others have mentioned, using walls to your advantage can be great. You can get the bears to go in a straight line very easily by having your back in a corner and casting at a 45 degree angle. If you're fighting a walling mob, you can even use the walls they make when they try and box you in. A single string of bears can be very devastating.
using bears and maximizing their dmg output is to use the environment around you to your advantage. putting your back against path blocking objects not only seems to stream line the bears but also increases their range as well. The odd thing I have found with bears is cast box, It seems to take place behind your character. This also has its uses if you are out int he open and something is approaching you from behind you know you will get some damage onto it. But when you have your back against a path blocking object it seems like the cast box is pushed forward so bears start spawning jsut slightly ahead of you.
I think this was done so if you where up against a wall you dont see zombie bears acting like ghost bears and passing through walls