If I might throw in my two cents as well, it's actually incredibly useful, provided your character is in an environment that would allow for full use of your semblance. Say for example you managed to catch your opponent at night but don't want to kill them, you could use your night vision to dart in and out, scoring light attacks that would allow you to wear the enemy out overtime, though the blows themselves will be nothing compared to the mental toll such attacks take. The fear coupled with pain will make them erratic, paranoid, and unorganized, their moves would become easier to read seeing as they themselves can no longer think straight. It would make going against your character in a dark place a true nightmare. That's actually how I intended to have Isaac fight when in the dark, he'd use his infrared vision to creep in, tear into an opponent with that wicked weapon, then slip back into the shadows as they bleed out, leaving their imagination to fill in the gap for whatever horrible thing just hit them.