saw a plethOra of mistakes imo.
You never got monks as a general. Even with the crystals.. monks are still nice to have.
You never got a single citadel upgrade. In fact, your whole team didnt get a single upgrade until about 30 min into the game even though you had warscore 10 around 20-25 min in.
Me personally, I never get speed upgrades on oak as you don't really need them. Surge + penitence is enough to catch people. As for running away, no need. Shield rank 3 is long enough to caplock something and teleport away. Impossible to be interrupted.. you are literally unkillable after lvl 8 (i usually get pen 3 first).
You seem to want assassin oak. Here is generally what I go, and I've had pretty huge success this last week or so since I started oak.
1. Pen 1.. not very useful atm.
2. DJ 1 .. nice to get back some mana / hp
3. Shield 1.. meh
4. Pen 2.. still not terribly useful as you have no mana
5. Surge .. we're still worthless due to no mana
6. Shield 2.. nice to escape or save someone
7. Pen 3.. mmm, this is about the time I go back to base to get helms
8. Shield 3.. woo not dying
9. Save
10. Surge 2, Pen 4. OMG
11. DJ 2
12. DJ 3
13. DJ 4
14. Save
15. Surge 3, Rally. OMFG
16. Last stand (not always)
17. SP 1
18. SP 2
19. SP 3
20. Shield 4
I usually don't do anything until I shop, unless there is an easy opportunity. I open by getting monks, botf, and wait a sec until I can afford a teleport. I wait until 3250g to go shop, and spend my time killing creeps, and going to cap mid and the flag in the lane I'm in. First time I go shop is around lvl 7. I get plenor and vlemish helms. Now you can spam surge and pen 3 a lottt. Next time I go shop, I get unbreakables, and make sure I have 3 tele's and maybe a caplock or two. I'll also trade my monks in to get high priests or bishops (depending on if there is another general, and whether he is getting high priests or bishops). I've gone several games up to lvl 15 ish with nothing but 2 helms, unbreakables, and bishops. I tend to save the rest of my gold at this point to get more teleports, sigils, caplocks, and creep upgrades. Lvl 10 is when the rape really starts going, and if you reach 15, you're pretty much unstoppable. Surge 2 on a creep wave will kill them all, so it's a great way to farm.
I will usually penitence someone, surge, then run after them. If they teleport right after I penitenced them the first time, I'll take note and save it if I know I can block them in somewhere and use penitence to interrupt the teleport if they have one.