I would like to come back to the PoF argument, since I think that is a not a correct example:
Ftaghn stated that while the fire is the actual target, the blasted individual's MR has to be penetrated. The fire being the target is not as obvious as you state it, since the blasted individual also needs to be in range and therefore might very well be considered the target. I do agree that the blasted individual's MR has to be penetrated, but I don't think it's the reference for a Warding spell.
I like to see a Ward as a wall that only exists for the thing warded against (so a Ward against the Fay only blocks Fairies, but not Demons or Grogs). If I create a stone wall, nobody is suggesting that it has to penetrate the MR of a Fairy that happens to want to walk through it.
So IMO, if the ward is in place it doesn't have to penetrate. And you cannot use a ward to drive something out in an active fashion (that requires other Rego effects).
That's the very problem I mean - the target from the point of view of the spell guidelines is not the target of the spell from the point of view of the caster. Were you to use Creo Terram to create a boulder 10 feet above someone's head, the distinction gets a little clearer - the boulder is clearly the target, and the range is the range to where the boulder can be formed. That it will then fall and brain somebody (assuming it penetrates) is incidental, the same spell could be used to block a doorway or dam a small stream.
The problem there (and it's more or less the analogy I use in my head) is that a stone wall is physical; the ward is immaterial. Creating a stone wall doesn't need to penetrate to block someone, but it does need to do so to harm them. It also doesn't block attempts across the wall, though for an hermetic mage you would need additional spells to allow you to sense across the wall. A ward is a wall which only exists for the target and that's why it needs to penetrate. The fact that levels of Might are built into the spell are a legacy effect from 4th ed where the penetration was the casting total - for 5th to make sense internally, I feel a flat guideline makes most sense. How would you feel if that were the case - that an apprentices ward could keep out a minor drake but an archmages, by dint of being the same level but far higher penetration, could bar the way of a great dragon?
And yes, you'd definitely need other Rego effects to actually drive something away.
I would like to add to Fhtagn arguments.
My point is Paris' argument is not acceptable, because the blasted individual need not be in range for a PoF-like spell. You could create a fire in a damp stone tunnel that last for a Sun duration, (sustained by magic) .When people "just happen" to try to get through, you would need to penetrate their MR to burn them.
A Pilum of Fire is just that: it create a fire that does damage. The fact that it take the form of a Pilum and need to be throwed, is just cool and is a cosmetic change.
The exemple of the PoF proove the non-sense of a reading of wards not needing to penetrate, and also the non-sense of deniying wards the use of Arcane Connection if you follow the core book rules. That's all true if you want to make a good reading of the rules. If you want to continue playing according to your view of what is a ward, I think it's perfectly fine to do as you wish.
About that part, I've written something that may add light to the comparison between wards and walls.
Why has the MR to be penetrated? Because you're creating it at the location of a being with MR, which'll try to stop any magical effect cast there.
Think of a MR being as a "no-magic zone"