Torp, basically: yes, that is a good build.
However, like me, you will suck when you are dismounted. Because of 0 athletics and 3 if.
Now don't let people fool you, Sarranid is good, but certainly not best.
Best low cost horse: Palphrey/Steppe Horse
Best cost/efficiency horse: Courser
Horses which cost more on your own preference, Cataphract is probably the best armoured one overall.
Sarranid Horse is the best if you want a high manouvre horse.