Baldur must either become deadly or be able to target enemies to become more widely used.
As he currently stands it is giving AI control of a critical element of your attacking team. Baldur easily falls into the trap of hitting a defender with riposte up (mainly Sif) which you would not do in most circumstances. Nor is there any certainty about targeting the badly wounded for a kill. Steady damage is nice but minions can give you a steady 250 damage to the enemy team and they act as pseudo healing for your entire team rather than just Baldur.
Baldur is one of many recent heroes that have great concepts but fail to be truly effective in execution.
Yes, I know that there are now real counter-minion heroes so minions are not a perfect solution but remain more effective than Baldur IF you are able to choose between the two options.
@Tidyup’s proposal would also work wonders for Baldur’s appeal.
I believe the obstacle to this is that it adds a completely new effect to Baldur’s special and changes his niche (to an excellent niche) which I doubt SG wants to do. That said, it would make Baldur much, much more effective.