This thread prompted me to read the 5e Grease spell. Here's the core effect of the spell:
To me, this seems a microcosm of the issues with balance in contemporary, non-4e, D&D play.
The effect is of (roughly) equal utility at all levels - being prone is a debuff that costs movement to overcome, and there is no general tendency of higher-level NPCs/monsters to have immunity to the debuff (eg flying) nor to have more of the resource used to overcome it (ie movement rate). (The fact that the 5e movement penalty to stand from prone isn't as severe as in some other editions doesn't change the fact that it is a penalty that facilitates mobility-based tactics on the player side, as well as an immediate debuff against close combat attacks.)
But the cost - the expenditure of a 1st level spell slot - reduces dramatically with level, particularly given Arcane Recovery, and at the highest levels of play Spell Mastery. (This is the contrast with 4e - an encounter or daily power is an encounter or daily power, and there is no particular class build that reduces this to a negligible resource cost.)
It therefore seems to me that this ability is broken, and to be honest obviously so - given that other characters (especially rogues and fighters, who are notionally meant to be useful in fights) do not get similar AoE debuff abilities that become trivial in cost as level goes up. The only way in which this spell seems not just as broken as the 3E version is that it is save-based - and so that aspect may, though need not, scale with level on the defensive as well as attacking side (whereas in 3E it was skill-check based on an obscure skill (Balance) and so almost certainly didn't scale).
This may be a particularly pointed example, but I think it generalises to other effects that generate meaningful debuffs at an ever-reduced resource cost as the caster gains levels. And given this context, I really don't see how there can be caster/martial balance.
When the grease appears, each creature standing in its area must succeed on a Dexterity saving throw or fall prone. A creature that enters the area or ends its turn there must also succeed on a Dexterity saving throw or fall prone.
To me, this seems a microcosm of the issues with balance in contemporary, non-4e, D&D play.
The effect is of (roughly) equal utility at all levels - being prone is a debuff that costs movement to overcome, and there is no general tendency of higher-level NPCs/monsters to have immunity to the debuff (eg flying) nor to have more of the resource used to overcome it (ie movement rate). (The fact that the 5e movement penalty to stand from prone isn't as severe as in some other editions doesn't change the fact that it is a penalty that facilitates mobility-based tactics on the player side, as well as an immediate debuff against close combat attacks.)
But the cost - the expenditure of a 1st level spell slot - reduces dramatically with level, particularly given Arcane Recovery, and at the highest levels of play Spell Mastery. (This is the contrast with 4e - an encounter or daily power is an encounter or daily power, and there is no particular class build that reduces this to a negligible resource cost.)
It therefore seems to me that this ability is broken, and to be honest obviously so - given that other characters (especially rogues and fighters, who are notionally meant to be useful in fights) do not get similar AoE debuff abilities that become trivial in cost as level goes up. The only way in which this spell seems not just as broken as the 3E version is that it is save-based - and so that aspect may, though need not, scale with level on the defensive as well as attacking side (whereas in 3E it was skill-check based on an obscure skill (Balance) and so almost certainly didn't scale).
This may be a particularly pointed example, but I think it generalises to other effects that generate meaningful debuffs at an ever-reduced resource cost as the caster gains levels. And given this context, I really don't see how there can be caster/martial balance.