Quote Originally Posted by Morollan View Post
To use your analogy, someone casting a non-subtle spell is 'merely walking along'. Someone casting a subtle spell is spending resources (sorcery points) in order to effectively achieve the same result as a stealth check. I don't see any need for additional hoops to jump through.
No. Casting a Subtle Spell is walking along without waving your arms around and holding a conversation. Casting a Subtle Spell lets you attempt to sneak in the first place, so to speak. It doesn't mean you automatically succeed. I can see where you're coming from with the resource expenditure, but what I see is that resource being spent to furnish the opportunity, not to hand the desired result on a plate. Bear in mind the other benefits, beyond deception, of Subtle Spell; casting whilst bound, or casting in an area of Silence or gagged, for example. These are "freebies" that are furnished by that resource. Deception is not, necessarily (or explicitly), granted (unless using XGtE, as conceded earlier).

Quote Originally Posted by sophontteks View Post
The additional effort is that you are using your action to cast the spell in opposition to doing something else. The idea that an action must be spent doing something every round is only relevant during combat and its pure meta knowledge anyway. Rounds only exist for the ease of running combat mechanics and don't exist in RP. Without any movements or sounds during the casting I have no idea what the deception roll is hiding. Your decision is running in opposition to the abilities effects; deception check must be rolled to hide the tells the ability explicitly removes.

From the characters perspective there are no rounds. Everything is played in realtime. Characters are not remaining still while casting a spell, they have free movement and the ability to continue reacting to their environment, including dodging and parrying attacks. The concentration involved in an "action" isn't very limiting. Wizards aren't going through some form of mental constipation when they cast a spell. Its very fluid and happens within 6 seconds or less.

In addition, look what sorcerers give up to have their metamagics: very limited spells, loss of other useful metamagics, using a very limited long-rest resource. You are nerfing them very hard and I doubt many players would be pleased to build a subtle caster under these conditions.
To expand my list of "Things you can't do whilst casting a spell", then;

- You can't cast Alarm (casting time 1 minute) whilst searching for secret doors.
- I would not allow you to cast Awaken (casting time 8 hours) whilst foraging or drawing a map while traveling (couldn't find a specific reference for this one, so this is a personal GM-call).

The point is that spending your Action every round to cast a spell with a cast time of longer than one Action is also representative of precluding doing anything else of significance during that time. Whether you're in combat or not. You don't stop "spending your Action" just because you're out of combat; you're still expending the same effort to "cast a spell" for the duration of the casting time. Yes, you can walk around and generally interact, but at the same time you are also casting a spell, utilising your concentration to do so. It's worth bearing in mind that whilst simple activities and object interactions don't require an action (e.g. opening a door), more complex tasks e.g. something as simple as opening a stuck door (reference: PHB pg.190; Other Activity on your Turn) or doing two such things within the space of 6 seconds, would be beyond the scope of performing whilst casting a spell simultaneously. Heck, as mentioned before, you can't even move 60ft (for your average Human) in 6 seconds whilst casting a "normal" spell. That's not that fast a speed to be travelling; I could roll a cigarette whilst walking that fast, but a spellcaster can't cast a spell at that pace.