They're taking the hobbits to Isengard!

To me it comes off as sloppy language at best, and confusing at worst.
It requires a lot of context to make sense, and thus would not work in this sentence.

Settings where it's passable to omit the "på" from "se på":

"Hun ser aldri (på) nyheter."
"She never watches the news."

"Han sovner alltid når han ser (på) TV."
"He always falls a sleep when watching TV."

In both cases it's no longer a description of a single occurrence, but treated more like a phrasal verb describing a habitual action. And the second example still grates me a little. ;)

Bottom line: You're safer to avoid it, especially in writing.

That would be the translation of "Hva ser du på?".

"Hva sier du?", yes.

There is only one present tense in Norwegian which can be translated, depending on the context, as Present Continuous (is seeing) or Present Simple (see[s]).

However, some sentences sound silly in Present Continuous. For example, En jente liker en gutt would sound silly if translated as "A girl is liking a boy". The same applies to Jeg ser ei jente which could mean you're dating a girl when translated as "I'm seeing a girl" but it actually doesn't carry this meaning in Norwegian.

Note that there isn't an auxiliary verb ("to do") in Norwegian present tense that you have to use to make questions or negate something ("Do you have..."/"You don't have...") but you do need to include it when translating to English, otherwise the sentence won't make sense.

Hva ser du? --> What + see + you? [literal] --> What do you see? [grammatically correct]