Some players house rules this requiring a ritual spell to dispell a ritual spell. Besides in wizard's war context, breaching this spell if the whole covenant is not your legal target may be considered depriving your (out of WW) sodales of their magical property, thus giving ground to you being Marched.
The enigma's gift: yes sure against a magus it's efficient... or not, because it's one of the spell you certainly will learn, if only to have a Magical Resistance mastery. My magus did it even if vim is nowhere my strong point. Having a decent parma magica + a bit of vim, doubling it means penetration may be an issue. Besides, if you succeed at sending your opponent in twilight, you have not won anything. The month of wizard's war may pass, and you gain nothing. Yes you may have stolen him, but you will face retribution if needed, and this time you may be the magus surprised because nothing in the game prevent anyone to be almost able to penetrate magic resistance of anyone.
Magic items for the poors with a lot of penetration (charged item), or penetration multipliers, mundane traps, political traps...
Nowhere is it sure that he will come out of twilight in the month, nor if he goes out, does the rules say he reappears exactly where he stood while he was sent. And if he comes back having understood, he may have been changed by the twilight, and if warped enough, maybe even learnt the spell which sent him in twilight, and maybe even had the mastery magical resistance won by a positive experience. It is not something I never have seen because it makes a lot of sense for the SG to say "you understand why you went to twilight, learn the spell, and learn how to never suffer it again"...
The magic sytem with the "ON/OFF" effect of parma magica doesn't give the game a "fantasy fight" feeling. We are nowhere near the fantasy books or stories in Ars magica. Best way to kill an opponent is to stay hidden in your tower, behind an aegis, or better in an unknown location, using an arcane connection to trigger a spell with an arcane connection.
You certainly can use a wizard's communion process so that your "killing spell size=50 (or (C))[/size]" level 50 is only counted as level 5 for a +45 penetration bonus (and you can maybe have a x5 multiplier... and if you have taken the time to prepare yourself you certainly have a mastery penetration of 1 (or better 2), and should by principle have 4 or 5 in the ability itself).
Against such strategy, the other will use one and certain strategy: be somewhere where the arcane connection is cut: magical realm, twilight, arcadia, some regios (depending on your saga principles on that points).
Ars magica is not, and I think will never be, a fun game about this thing. It may however be interesting to treat what happen next: how will you deal in the next tribunal the charges of breaching the code, or the new retributional wizard's war, or the political moves of the amici of your ex-rival, etc.
That's only my opinion.