Are Ti saddles really much stronger than solid cromoly. They are certainly lighter but the strength to weight ratio of metals is very comparable. (unless you compare top grade ti to lowest grade "hi-ten" steel). Some lightweight saddle use hollow rails which are not for heavy riders.
Where is your seatpost clamp on the saddle rails. For maximum strength they should be clamped in the middle. If they are clamped at the front, you may benefit from a seatpost with more layback.
You will want to retain your seat position, just move the clamp back in the saddle rails. Use a plumbline to note the position of the saddle nose in [x,y] from the centre of the bottom bracket.
Dont move your saddle AND bars as your mechanic advised, this will alter the saddle-pedals configuration.