If you let haley alpha strike you before she feats, you are basically ****ed. So the goal when trying to win the matchup should be to make her feat defensively, you can do this by either having a longer melee threat range or by drastically outshooting her(hard with decel).
I think expecting to beat haley(best cygnar caster) with sloan(worst cygnar caster) is not realistic unless you really outplay your opponent.
I do think that kraye, seige, ecaine, both strikers and nemo3 can all fight her in an even matchup. Do you play any of those?