Speed mods on most of the tanks are useless. (away from some exceptions like ST-Han. Of course you might need a little to Taunt quicker but you don't want to lose precious survivability just for that. Best to mod secondary speeds based on your needs, depending on your enemies)
1. You want your Taunt to stay longer,
2. Sun Fac already attacks and dispels many times thanks to his counter attack anyway.
Maxed out SF (Max gear and Star) without any mods have 26k Health / 37k Protection
So stacking % Protection mods would be wiser. (Especially since that Primary Protection can reach 23%, while Primary Health can only reach 5.88%)
As a General Info: With 4x Primary Protection Mods you will reach 71K Protection on SF even without any secondary mod bonuses.
a. Which is not necessary since you might wanna get Tenacity on Cross, he has base Tenacity of 35% + a 24% Tenacity mod will help a lot to avoid Stuns / Shocks / Daze's that stop him from being effective)
b. Depending on your enemy composition if you have a lot of Wiggs / Droid team enemies "Crit Avoidance" on Arrow mod would be useful too, but I doubt there are many Wiggs - Droid teams left (that rely on stacking Crit Chance - Crit damage) at the moment (thanks to Zauls), so probably Protection might work better there.