TL;DRChange the font with the support of non-Latin based languages.
What ?So in the light of current events of the GUI redesign, I want to propose you to think about changing the default font in the game. Titillium, the font you use, is a great font made by Google, but its support of languages is very limited. Basically, it includes just Latin and Extended Latin character sets thus covering the majority of European languages. But the rest... Having the Russian as my native language and living in Israel, but playing in English just because the secondary font you've chosen simply ruins the experience of the game (I'm a visual guy), I have mixed feelings.
Let's clarify. To be fair, I have to thank you guys for having a secondary font at all! Many other games, a lot of games to be fair including multiplayer games, simply don't have any support for any non-Latin based languages at all. They print blank spaces instead of letters. For example, in Guild Wars 2 playing in a Russian guild with my Russian and Ukrainian friends, we weren't able to talk to each other in the game chat. Typing in Cyrillic is still impossible there forcing Russian players to use third-party voice apps exclusively pushing conversations out of the game and drastically changing the experience. NCSoft says they protect English speaking people so they could read everything in chat. How exactly this protects them from German/Polish/Portuguese/French/Norwegian and other non-English speakers and even transliterated with latin characters Russian speech is left unclear and unanswered. So thank you very much, Wube, for supporting non-Latin based languages at all.
Why ?But there should be the bold but, the secondary font (is it Arial?) doesn't look like Titillium and changes the feeling of the game. It has a very distinct look and feel. It's wider and less dense making Russian texts (I've only tried Russian, but I think this applies to other languages as well) even longer than they tend to be, expanding the small text containers. The only common trait is that it's also humanist sans-serif (it's like changing your cat pet with a sloth on the grounds that they are both mammals). It seems like a small feature, but I'm sure the graphical department knows very well how the font is important for the visual style of the game and its consistent look, and how the bad font choice may ruin the experience from the game simply because it's hard to read or it doesn't fit the style at all.
SolutionsIt wouldn't be fair to not propose some solutions.
Droid Sans made also by Google. It looks very close to Titillium, although more round and a little bit vertically squished in its smaller spectrum of sizes.
DejaVu Sans is a great font with the support of a large portion of languages including Cyrillic based languages, Greek, Hebrew, and Arabic (if you ever consider including RTL script support). One of its 9 styles, namely DejaVu Sans Condensed Books, looks even more similar to Titillium, a little bit smaller though so you could consider to increase it by 1 or 2 pt.