Master Summoner is internal tier movement mostly. Tier 2 is already an extremely powerful tier. The big issue with Master Summoner is that you can just spend every turn summoning more monsters with your extreme uses/day and shutting down combats with extremely large crowds of monsters to use as everything from utility to meatwalls to damage sources, but normal Summoners can already use Summon Monster -> monsters attack, then on next round hold action summoned monsters attack -> Summon Monster again -> more monsters attack and get 2 packs of monsters attacking each round. I guess if you have the benefit of concealment you can spam summon monster to make a large pack of enemies before walking through a door to nuke everything. On that note you can also lend items to your summons to make them uncommonly dangerous. Lillend Azatas for instance are basically 7th level bards, which means if you hand them Dervish Sikke, Three Reasons to Live, and Banner of the Ancient Kings they will do Inspire Courage +5 instead of Inspire Courage +2. Similarly you can hand them Page of Spell Knowledge or Ring of Spell Knowledge to let them cast spells they don't have as spells known.
For Magus, the most potent archetypes are Hexcrafter (if you abuse SoL hexes and the like) and Beastblade (if you make up for loss of Knowledge Pool), since it's made for action economy abuse. Achieving Tier 2 is pretty doable for any Magus through either abusing SoL effects or raising damage to something that will reliably OTK (One Turn Kill) enemies.