Hi Kazin,
Lot of things were changed with 5th ed. I guess changes will always divide people. Personally I am very glad we got the 5th, and the revival of Ars in general, but I started some editions back and my current still-running sage was run with 4th ed rules when 5th was published, which is why I haven't yet completely changed to the 5th edition rules. We are getting there gradually though. One of the things we took in immediately was the new magic system - it really is much more stream-lined and accessable - and that meant redefining what was and what wasn't possible with magic. One of those things were the former dual Ranges/Duration/Target of most spells (one of them being the permanent healing spells)- a remeniscent of this is found in the Flexible Magic Virute or the House Mercere chapter in HoH:TL. The need to make a ritual to make things permanent took some getting used to, but now I am actually quite fond of it. I reckon it is a matter of preference but I do find that that anything as epic as fusing an arm back on requires a ritual is quite fitting. And still very impressive and jaw-dropping.
Mind you it is still possible to instantly close any wound, even on a battlefield, impressing any witnesses as you please. Even if the standard spell in the core book only describes the ritual versions of instant-heals, you can with spont. or formulaic magic still instantly heal wounds with a duration. That would make you able to fight on, and scare the living daylights out of people, but after either Diameter, Sun or Moon time the wounds would reopen. But hopefully you will by then be safe - maybe even have the vis and know the proper rituals to make a permanent healing. And most of all, the people you might have intimidated will not be around to see you arm fall straight off again. Off course putting an arm back on, because you need to add duration to the spell level, requires a higher mastery of the involved Arts, which isnt that unfittingly either.
I have had my most issues with the general effect of vis and earlier I started a threadon this with a discussion on the level of the bonus on vis boosts in 5th ed. I couldn't really see the need for reducing it from 5 to 2 when boosting your spells - for me it isn't a question of how much is doable with vis (the powerlevel) but that I missed the nice touch that rules and setting came nicely together. Ingame magi do not talk of levels - their reference is Magnitude, and I think it is great to have terms to use in game (as opposed to between players) that have a reasonable background. A Magnitude was both the needed vis in a ritual and the added bonus of using vis in your regular spells, thus the magi could use this term. The discussion in that thread was mostly on the powerlevel more than the fusing of setting and rule mechanics. For now I have kept the 4th ed +5 to spell rolls and decided that I would rather keep the old bonus, bc of the setting effect, and then adjust the powerlevel by controlling the amount of available vis. You might opt to do the same - but out of the power of vis and what is possible. For your magus it would also be easier to reach the higher level needed to fuse and arm back on, with the added Duration, so a higher effect of vis would certainly help you out.