faster run speed
finishing moves which are based on monk level for DC, a few handy ones -25% mana and earthdragon
Here is what you gain for 18 druid
Level 9 spell slot - snowslide which is runspeed basically
2 core enhancements, sla storm of vengeance, 1 dmg 1d6 sneak and prr for bear
(Could easily build tankish bear if you go for the prr. 20 bear, 15 earth stance, 15 shinatao, 15 flowers ed, 14 blue slot very high dodge and AC, threat from earthstance, spell threat from roar)
Storm of vengeance SLA is important because I wouldn't have it prepped otherwise and it is an important spell for debuffing for CC with annual susurrus.
My original build had thought of taking the entire evocation DC line. I took just one to open up ED twists which the -10 to save proc is the most vital. I haven't found that missing that 2 dc for 2 feats have made a difference yet in EE. Done Wheeldon but not stormhorns. Druids are feat starved, I opted for dodge and empower healing on the pure 20 druid. I do switch to water elemental if CC isn't landing and take one for the team. Monk splash for CC with stances I'd gain an additional 4 wisdom from water stance. Still have 5 wisdom from enhancements, 2 nature's warrior, 2 herald, 1 human with the option to add another 2 from boosts if I wanted. This splash I would gain 2 dc if I desired to be in water stance. I run with a bard 90% of the time so I do get inspire and song which might be why I can get away with saving two feats.
Note on dodge and four good legs. I just ran EH tor last night for farming some helmets and not having this was noticeable. Random giant knockdown, jarilith trip, dragon tail swipes all put me down when NONE of that did before. I quickly got it back after that run. Getting knocked down is the number 2 cause of death. #1 is failing reflex saves. Monk splash addresses this.
I would consider heighten a needed feat for lightning bolt SLA, sunbeam for blinds, a lot of DC for jaws of winter and gain the same 1 dc for earthquake.