Multimode problem - is it still an issue?

By design, Virus TI patches use dynamic allocation of resources. The resources are mainly memory (e.g. to store the recording of a sound to be repeated in a delay effect), and DSP cycles (every cycle is one step in the calculation of a sound or an effect). Each patch has different complexity and therefore taxes the TI's resources differently. When the next note to be played cannot find enough resources, the synth engine picks what it thinks to be the least important playing note, stops it, and gives its resources to the new note. This is how note stealing happens. As opposed to synths with fixed polyphony, in the TI note stealing is influenced by the amount of parts used, the complexity of the patch used by each part as well as the amount of notes played by each part at any given moment - in other words, even with the same sounds, different arrangements result in different note stealing behaviors.
Avoiding note stealing depends on the situation, for example, in the studio you can let note stealing happen as you build the MIDI arrangement, but when you get to the point where it's time to commit to tape, you can multitrack and overdub separate parts and even separate notes, to make sure that each one is heard. In a live situation, you have to build your setup to fit the song. Don't stack up too many layers, voices, oscillators and effects on one synth. Avoid the more complex oscillators and try to delegate effects to external processors. Don't use unison without a good reason. Also note that the snow has a little less than 50% of the resources of the rest of the TI family, but maybe 2 or more separate snows will give you better results than one TI that is supposed to do everything.
Hope this helps.