I use druid level 8 spells for premonition and storm tower. The latter is extremely good in some situations. And I'm not a big fan of summons, and in the parties I were playing there were a big waste of time. Planar binding on sorcerer level 6 is enough to get a good summon for Hades farming, you just have to cast it a few times to get something good.
You say the stat is a very easy choice but don't actually say which is better, at least not that i can easily tell. You then also say mnk splash is only worth it if you go Wisdom, which you do.. so i don't see why not at the loss of 1 SP. And does the Wisdom then act as the DC stat for all sorc spells as a HoS? Is there a better CC then the other right now?
Regardless of CC you use the highest between wis cha for spell dc. Wisdom is also a better stat than Cha (it adds up for will saves)
As a rule you should think of Druid as a better CC for herald as it have more skills points, skill options and hp.
HOWEVER this build in particular took advantage of the Extra spell known feature, that only CC sorc get. This advantage is particularly good as it allows you to get more spells - which was the objective of op.