Modus Veritas Duration 5/5:
If you use Helix spells, I strongly advise taking this one. When fully capped, Modus Veritas will only reduce the duration of a Helix spell by 25% as opposed to the 50% norm. Consider that Modus Veritas DOUBLES the damage of a helix spell 'tic', and that means you see a bonus of 50% damage dealt. Thats an incredible amount of damage for such a low MP cost, and has some devastating results if you stack it with other Scholars (see the Yovra video)
This Cat1 merit has got a lot of good press lately, but in the vast majority of situations you'll find yourself in on SCH, it's marginally-to-completely useless.
First, it does not increase damage dealt by 50%. It can, possibly; but due to the discrepancy between the random duration of helix spells, the way ticks are calculated at different times for every mob, and the delay between casting the Helix and using Modus Veritas, you will only rarely gain a full DMG+50% over a non-merited Modus Veritas.
Second, Modus Veritas has a recast time of 10 minutes, which is not reduced by merits. Assume an average Helix duration of 1 minute over 10 minutes, continuously recast immediately as they wear off. In this situation, Modus Veritas adds a whopping 5% damage to your Helix DoT; hardly worth the merits.
Third, I wouldn't go dumping merits into Modus Veritas based on that Yovra video until you know you have 8 other SCH + the considerable amount of support necessary to pull it off. Besides, for anything but AV, it's a waste of effort; and as soon as somebody kills AV with it, it'll get patched.
All this being said, all the Cat1 merits besides Helix MACC/MAB are rather lame. At least the Sublimation merits are kinda useful for 100% of situations you'll find your SCH in.
Also, don't let anyone fool you; Enlightenment(x1) is the best, most useful Cat2 merit available by far; it's the closest you'll get to meriting Strategem Charges. Stormsurge(x5) is a given, but it won't save your ass on a daily basis like Enlightenment will.