There are times, and it happens with almost every game released, when the description of a certain game mechanic or ability is ambiguous enough that players are left unsure of exactly what it does in certain specific game situations. When the devs aren't handy to provide direct clarification, there is a certain subsect of the gaming population that likes to engage in theorycrafting, grabbing large chunks of data to see how closely abilities work in practice to the numbers set forth on their tooltips or in the patch notes. Among the only solid theorycrafting I've seen so far for Tabula Rasa is from the folks over on the Tabula Spot forums, where among the many things they're working, is on figuring out which Logos abilities stack with Rage.
So far, the results don't look terribly promising. Neither Lightning Discharge nor Shrapnel show a statistically significant difference in damage when Rage is activated (and here we seem to be talking about the nerfed Rage on the PTR). This seems to conflict with the Rage tooltip, which says in part, "Utilize the power of Logos to increase the damage done by your attacks." Interestingly, while Rage doesn't appear to work with Logos abilities, it does work with hand-to-hand. Methinks they should consider amending the tooltip to reflect the way it actually works.