Treantmonklvl20
Explorer
Magic Missile is a terrible spell to break enemy concentration with. Magic Missile upcast to 4th level will do about 21 damage, which won't even break the generic DC 10 concentration save. It's only really good as a hail mary to stop several spellcasters concentrating on a spell at once.
No. This is a terrible suggestion. Unless you do one-encounter workdays against single super-casters, you will not win this race.
This is another terrible suggestion. Unless you know for a fact they're going to be casting some turkey spell like Witch Bolt or Otto's Irresistible Dance at the archer, it's a very acceptable price to pay. In a recent module, I counterspelled the counterspell of an archmage who was throwing up a shield; this allowed the paladin and ranger to one-shot them on the first round.
Also, if your DM rules that casting counterspell (or any reaction spell) while in the middle of casting another spell makes you lose your spell, they are screwing you over with a houserule. Don't let them get away with that.
Toll the Dead requires a Wisdom Saving Throw. It will not be better than Fire Bolt (or any spell that targets ranged AC) most of the time unless you did something like put on a Robe of the Archmagi and Ioun Stone of Mastery while also getting really lucky with a Deck of Many Things.
I pretty much agree with every point Rofel makes here. I would add though that it is a good idea to have a damage cantrip that requires a to hit roll, and another that requires a saving throw. The latter are useful if you are in a situation where you would have disadvantage on an attack roll, or the enemy has a high AC.