The other day I put up a post asking for suggestions for good Magery 0-requirement spells for a DFRPG game. I got a few of them.
A number of them, though, have been offensive - Flash, Glue, Stench . . . generally, I went for utility spells, ones that are useful to put up but either have a long duration (Continual Light) or a long effect (Ignite Fire) or have a reasonable cost-to-duration (Mage Stealth).
The offensive ones? Great spells, if you manage to get them off.
Here are some practical issues I see:
For non-Wizard, non-Bard templates, skill is going to be between 8 and 11 for a 1-point investment in a spell. Most of them will be the lower - it's the Thief that allows for a whopping 11 for 1 point.
A character with IQ 11 and Magery 0 needs to put 20 points in a spell to get to a reliable and cost-discounted 15. If you're putting 20 points into a single spell, you should probably be thinking you are overemphasizing your minor at the expense of your major. Should a Knight dump 24 points in getting a 15 in a spell or raise ST by 2, DX by 1, skill by up to 5 (6 if you dump the spell entirely)? Odds are, you aren't adding more than you are taking away. Points are zero-sum. So you either accept a low skill and success rate, or dump in points to succeed more often at the expense of other things you can do well. That could be two to four well-shot arrows, a Feint and a sword swing, four blows from fists and feet, a backstab, etc.
For a different caster type, these are smaller issues - you're looking at a 12+, but then again, you need a solid reason for an offensive spell based on IQ+Magery 0 when you have IQ+Power Investiture 3+ on tap, instead.
With a low skill, odds are you are going to fail fairly often.
Skill 8 = 25.9% of success.
9 = 37.5%
10 = 50%
11 = 62.5%
Those aren't great success rates in a time-critical application.
Failure will cost 1 energy.
Success will cost the full amount.
Odds are you'll pay more than the full amount to cast the spell.
For most templates, casting time will be double. Skill 9 and under doubles casting time (per Spells, p. 10).
For a lot of spells, this "merely" makes a one second spell two seconds. But now this spell must be worth taking two turns away from other actions the PC could be doing.
Again, you can remove this issue with points . . . either with improved Magery, or IQ, or just putting 2 or 4 points in each spell. But the same concern applies that I mentioned above - what are you not doing with those points that improve your profession? And if you're doing to pull lenses from DF and go for the Wizard lens, you should be eyeing it as a whole, not in terms of a few Magery 0 spells that could help.
So from a practical standpoint, low-point investment spells for Magery 0 characters are going to fail often and cost a lot. I think utility is better for them. From an efficiency standpoint, if you're going to invest points to get past these practical issues, you're starting to get away from what you do better than anyone else in order to half-ass something less poorly. I think that's probably a mistake.