I made a new topic to gather information about the new Vision fields so that I can keep the first post updated, instead of having to search through the old thread:
It seems that you have to replay the unlocker fields if you want the Vision field it gives, Looming difficulty is enough.
EDIT: The list is now complete and doublechecked, if someone wants to transfer it to the wiki it would be great.
Many thanks to @bilboCGL
V1 -> K3 Looming
V2 -> P1 Looming
V3 -> C4 Looming (MP only)
V4 -> D5 Looming
-----------------------------------
V5 -> L4 Looming (MP only)
V6 -> U7 Looming
V7 -> Q4 Looming
V8 -> J5 Looming
V9 -> Y6 Looming
V10 -> N6 Looming
V11 -> H4 Looming
V12 -> X7 Looming
V13 -> R6 Looming
V14 -> G3 Looming (it then goes on hextile F)
V15 -> A5 Looming
V16 -> G5 Looming
V17 -> W4 Looming (MP only)
V18 -> J4 Looming
In these new vision fields there is almost no need to enrage, enraging only vew (nice typo for very few) waves at the beginning is enough 1g1 gem or so...
Have you noticed the "Walkthrough thread for vision fields?"
V 18 strategy-start combining gem till you have a level 5 and a level three. Put the level 5 in the topmost tower and put the three in an amp just below. when you have enough build a tower below the amp with an amp to the left and bomb the tower to south and replace with amplifier. move the level five which you may have leveled up by now to the new three amp tower. beam and freeze giants aggressively and they will not bleed. Some reavers and swarms will get through, but with all mana gain it won't be a problem.