Wyssans, speed of light, byronna's, flesh of stone , miasma, iceshard blizzar, hand of glory, and all that affects units modify all the unit stats, so it affect mounts of every kind.
The weird case is upon certain spells that focus on heroes. Like Savage Beast. You target one hero and the model gains a benefit. So where to apply? All the model of the targeted hero? Only the hero stats as I guess is intended?
I can use both interpretations and be equally reasoned. This is the magic of warhammer rules!
Character only: It targets a Character, it boost the character stats.
Whole model: It targets a Character but it says the benefit applies the model choosen. And the definition of model is the miniature.
Example: A orc chariot is a single model with 3 set of stats.
- Chariot stat with Strenght, Toughness , Wounds & Armour Save
- Boar stats with M,WS,Strenght, Initiative & Attacks.
- Orcs with WS, Strenght , Initiative , Attacks, Leadership.
So what to apply? Only character stats or as readed the "targeted model".
Because skink chief on regular steg with savage beast of horros applied to the model...
4xSkinks with S6 and 4 Attacks each
1x Stegadon with S8 and 7 attacks
1x Chief with S7 and 6 Attacks.
Well I just use only the hero stat because I feel it the real purpose of the spell. And what I never want in a warhammer games is an endless rules discussion

What do you think? Only hero stats or the whole model?