Soul burn is an excellent poison (and it should be, too, rogues are the kings of damage and their poison should be highly damaging) but this doesn't mean we couldn't have some different, custom poisons to use as an alternative.
I haven't spent any time exploring all the recipes but some high damaging, short duration dots (with lower initial direct damage) would be cool as well as some utility types, such as a very short duration slow effect of up to 40% for two seconds or something like that. Lower level versions could be available through lower level custom zone drops but the best stuff would drop only from the group zones and raid zones and not too commonly.
It's not like the rogue needs this, by the way, but if we're agreeing here that the only poison worth using is soul burn, because it's so powerful, then I don't see that as a good thing particularly.
Incidentally, I don't tend to use soul burn very often due to the fact that it wears off when I zone. The time taken to craft poison for my rogues (yes, plural

) is not worth using it all of the time, so I only tend to use it against the "not sure we can quite do this new raid mob we're about to try" moments. I zone a lot and don't play for extended sessions all of the time and the rogue already does more than enough DPS so doesn't need this poison. It gets resisted a ton anyway (which is fine).
However, if I had some other options, to do something that the rogue might not normally be capable of doing innately, I might spend more time using the skill. Not desperately needed, no, but it's certainly an interesting thought.