Welcome aboard.  I find just the opposite with bullets - that good jacketed bullets are superior to cast for deer.  I now prefer the Hornady XTP designs, they expand very well at low velocities.  
It is true that some jacketed bullets do not expand well - this was particularly true in past years before the current crop of excellent handgun bullets.  This is one of the reasons that cast bullets with wide meplats got such a good reputation versus jacketed bullets in the past - old jacketed bullets didn't expand and with small meplats didn't kill well.  That is not the story today.   I used LBT designs in my .44 and .45s, but the best cast design performance-wise was the Lee 45-250 FN.  This short bullet had a very wide meplat and killed small deer well, although I still prefer good, proven jacketed designs.  But if you prefer cast bullets and they work for you, by all means keep using them!