IMHO, the Roc is the best balanced of the canon Protomechs, because a point of five of them, is equal to a heavier Medium battlemech in terms of movement and firepower.
That's my own take.
To me, a point of Protos should move together, sharing a movement curve, and five Rocs is a LOT of firepower moving at 5/8/5, able to play offense without losing much, able to spread out to create a dangerous defensive line with mutual fires and cross fire potential.
So, here's the challenge:
Design 5 Protomechs, with the same movement curve, roughly equal survival and endurance, with different weapons to fill the different roles you see in a common 'trooper' type medium or heavier 'mech. Armor values can flex, depending on what other gear you give them, but they all have to be able to match one another's speed, and we're looking at brakets for comparison.
What do I mean?
3/5: This is the most common speed for Assault 'mechs. Your point has to be able to deliver roughly the throw weight of a well-armed, general purpose Assault 'mech such as a Battlemaster, which said assault 'mech has multiple weapons systems.
4/6: Most common Heavy mech. Comparisons to the Thunderbolt, Warhammer, etc.
5/8: a bit more flexible, this must match the throw weight of a 55 ton to 50 ton range with a 5/8 ground speed. (Classic 55 ton trio, etc.)
6/9: Low end Medium or high end light again. Points of comparison being the 45 down to 30 ton brackets, (Phoenixhawk, Valkyrie, etc.)
7/11: Mid-level Lights (30 to 25 tons)
9 or higher walk: 20 ton machines.
Pick your bracket, design your protos, post 'em here, and discuss which battlemech they're 'roughly equivalent to when working together in a point'.