I think it is quite clear that Assange is a high value person of interest in the legal sense. Usually, when sexual assault is the crime which is of interest, high value is when the alleged sexual assaults involve violence, predation and notoriety. This is not the reason in this case, but the full extent of the international legal tools at disposal are being used within proper discretionary limits. Also with his defense against these legal tools, Assange is using all legal tools properly at his discretion.
While the current standoff continues, Assange is, in a reduced but still powerful way, able to continue to lead Wikileaks, and the Syria files proves that the organization is still functionally sourcing and publishing leaks. Client states of the US which were nasty dictatorships have the most to lose with these leaks. Of course, the US also likely loses them as a client states as well, which may or may not be a bad thing for the West.
As far as the risk to "informants" goes which is a highly publicized issue, I think it is a fairly long bow to draw. The war(s) are grinding ones of attrition and a large scale leaks makes both sides extremely jumpy, because they have the same access to the same information, with enough of it with parts deleted or changed that they cannot be be confident of exactly who is the informant. Most terrorists just make a wholesale slaughter of all possible informants, quite regularly.