So recently a player queried my understanding of various general spells causing me to rethink. I played ArM since 2nd ed. so I may be out of date with some of my thinking; but I thinkI am current with my understandings though I pledged to check it out. So here goes...
1: Gen spells still use range duration modifiers?
e.g. Demons eternal oblivion range voice. At lvl 5 it removes 3 might and at lvl 15 it removes 5. (2 magnitudes used in range=voice)
2: Warding effects do not have to penetrate?
e.g. Ward against faires of the forest. At lvl 5 it prevents might 5 faeries from entering the circle, at lvl 15 it prevents might 15 fey etc...
3: Gen spells still do have to penetrate:
e.g. demons eternal oblivion. Having a low level version is more useful on account of the penetration effect. Indeed having a version where the might removed is lower than your penetration total is largely pointless (saving spell mastery options and sympathetic connections.
The RAW don't mention an exception for wards in this regard, so the official line is that wards do need to penetrate just like any other spell. Personally, I like a house rule where Circle target and Ring duration wards don't need to penetrate.
I think you're right on 1. The RDT parameters must still be factored in to the spell's effect.
Wards and general spells, as with other spells, must still penetrate. With general spells in particular, remember that once you've created/learned one it has a defined level just like any other type of spell, so the distinction isn't that important.
You'll likely get a few replies on the ward thing. The rules as written do not provide an exemption to the more general rule that spells must penetrate the Might/Resistance of those things they affect. There's no compelling reason why they should be treated differently. But some players like the extra punching power that a no-penetration house-rule provides.
If you are looking to apply a house-rule to make wards stronger I'd look at allowing arcane connections to be applied to boost penetration against specific creatures/entities. It's not something that can normally be done but in my experience it makes wards more in keeping with what I think they should be. Dropping the penetration aspect is a little like using a club hammer to crack a nut; it's just a little extreme.
Your calculation of DEO is off making me think that there's something that isn't understood. The guideline is "reduce target's might by level of the spell +10" from page 160. So, loosing two magnitudes for range voice, at level 15 it removes 15 points of might not 5 (base spell level is 5 so 5 +10 is 15). Parameters have already been taken in to account for the spells that are described in the books, such as demon's eternal oblivion you should be able to read the description and go.
Btw - it is worth noting that going by the wording in the book, a level 5 DEO would remove 13 might (base 3, +2 for voice)... For this reason we've houseruled the guideline to be +2 magnitudes instead...
The "+x for Range/Duration/Target etc" in design notes is always magnitudes. Because below level 5, each "magnitude" is the samen as level, meaning 1st magnitude (level 5) -1 magnitude (5 levels) is not level 0 but level 4. This is well described in the book, under the spell section IIRC.