
Originally Posted by
Turalyon
This is actually part of the issue. Rohana's sole purpose in the story is to give an info dump on Amon's motivation. It's exposition for the sake of exposition.
Sc1's Overmind is the sort antagonist of the same mould that Amon is cut from in that both are sci-fi archetypes of "aliens beyond normal-human comprehension". However, the difference is we get a peek at the Overmind in its element and get a chance to understand it. Granted, whether it ultimately worked is subjective but it is mightily helpful in getting a feel of it's motivation. Without it, the Zerg are really just some big bad to be defeated like Amon is. Case in point, is that if all we had to go on in Sc1 (as in no Zerg campaing) was Zeratul's and Tassadar's assessment of the Overmind's motivation (like it is with Rohana doing this to Amon in LotV), than the Overmind would clearly not be as memorable as it was. The Overmind's portrayal is partly the reason why Zerg is my Sc favourite race lorewise.
The same can be said for the UED since whilst they were more obviously shoe-horned in as antagonists out-of-nowhere, they were made memorable through the depictions of DuGalle and Stukov.
You didn't stipulate that restriction of keeping the key plot points at first when you asked about how Amon should have been portrayed. Even then, the key point of Kerrigan's redemption that you note is a dubious one in that it only occurs with any clarity in LotV. HotS is clearly not about Kerrigan's redemption and if it was supposed to be about that, it's terrible writing because of the mixed messages it gave.
Still, the problem with Sc2 and the paucity of Amon's depiction is largely to do with the fundamental aspect that Sc2 is not really a cohesive trilogy. WoL and HotS are clearly linked what with them largely being about Terran affairs whilst LotV is off on it's own tangent being somewhat disparate in comparison to the previous two. When followed sequentially, LotV sticks out like a sore thumb because it's story can actually occur and work without having to play or have knowledge of the previous two entries. WoL and HotS don't really inform you much about the situation leading up to LotV, since the one thing that does (the artifact plot device in which the whole story hinges around) came out of nowhere anyway in WoL and was in possession of the "evil force" already (Moebius and Tal'Darim).
The only conceivable way to improve this (nothing can truly fix the shambles in how this trilogy is constructed), with the aim being to reinforce Amon depictions above all else and without giving Amon the benefit of his own campaign, is to totally shift the focus away from all the Terran affairs that dominated WoL and HotS and have the Hybrids threat be front and centre. Mengsk should've been dealt with early, possibly in WoL or very early in HotS, in order to focus on the universal threat of Amon. As it is, the trilogy when seen as a whole doesn't seem to know whether it wants to be about local and comparatively small Terran affairs or the grandiose, mystical Xel'Naga God/cycle stuff. What with two installments being about the "small stuff" (Terran) and one installment about the "big stuff" (Xel'Naga/Amon) and that the side-tracks of Zeratul's visions in WoL and the Primal Zerg in HotS seemingly being shoved in without making much sense (although the latter actually serves to move the plot mechanically at the least), it seriously makes you wonder what their priorities were when developing this "trilogy".