I enjoy playing 1h + shield Cav because I personally find it more useful for supporting my teams Infantry, I very rarely TK or get a friendly killed by bump ( shit happens sometimes, every single player no matter the build has wounded or killed team mates on accident ).
When I approach a small cluster of enemies and teamates fighting, I line myself up to pass just past the enemy, not actually through them, this way I have more time to react to my team mates movements and the enemies, if at the last moment I can see I have a clear path to bump through and slash, I will, if not I will just try to slash the enemies at the edge of the cluster where I am passing by.
I have a similiar approach to when I see a 1v1, I aim to pass by the team mate and enemy fighting, watching their movements closely, if my team mate ends up turning his back into me and/or with the enemy on the opposite side I simply break off and either find a new target or turn around to come in for another ride by. If the enemy turns around my team mate and is on my side, I will usually attempt to slash rather than bump, because bumping him would put me closer to my team mate and raise the risk of a team bump occuring, unless I can see that I have a decent amount of space to bump the enemy.
The smaller the fight, the more surgical your approach has to be to help your team mates over hurting them.