When I replace a peice of armor or a different weapon for one that's clearly better, the stats on it actually go down. I have a lvl 52 equipped and was going to equip a lvl 56 one that literally has better stats but it stays goes down from 169k to 150.
I dont belive its a mistake, here is what i think.
You should not consider damage, but damage per second (DPS). So even if the lvl 56 item has higher damage, it might be slower and provide less DPS which is what matters. Alternatively, the lvl 52 weapon could have high main stat value (strength, dexterity, inteligence), while the lvl 56 maybe has none. Main stats are also a great DPS boost at lower levels.
That is really strange. Post this on official D3 forums. The sources have like 500 int difference and after equipping is less than 100 int difference. The wand/spear thing - maybe Magic Weapon dropped when you switch them? But this is something messed up