Okay, before we discuss tactics we first have t discuss the power disparity.
At the beginning of the invasion the IS and Clan forces each have a Mech that has a polar opposite on the other side: the Warhammer and the Hellbringer. Both Mechs weigh in at a similar amount (70 and 65 tons respectively) and both are designed and outfitted for a roughly similar role and both have a similar loadout (assuming prime Hellbringer)
Firstly, both Mechs are intended to fight primarily at medium to long range until the enemy is softened up for the killing blow. In doing this both carry a primary armament of two PPC's, and backing this up on each is a six tubed short range missile launcher, laser array and a pair of MG's for dealing with Infantry, but even here we are seeing the disparity already.
>PPC's
The Warhammer carries two regular IS PPC's that can do 10 points of damage and hit out to a respectable 18 hexes, but the Hellbringer carries two CERPPC's that are swatting targets with 15 points of damage each, at a range of a whopping 23 hexes, easily out ranging and gunning the Warhamer.
But what about the fallback weapons?
>Laser Arrays
The Warhammer can call on a well rounded array of two Medium Laser's and two Small Laser's, giving it a nice bit of fallback for dealing with anything that gets within its minimal range. Its a nice backup and can deter lights from getting cocky, or finish off opponents crippled by the cannons, with the ML's hitting out to 9 hexes for 5 damage and the Small Lasers out to 3 hexes for 3 damage. Nice? Well, the Hellbringer only gets three CERML... But these are doing 7 damage out to 15 Hexes - nearly as far as the IS PPC!
Well this is already looking bad, but what about the missile systems?
>Missiles
The Warhammer gets a SRM 6, a nice close ranged punch for ripping through criticals like no tomorrow. It is a respectable weapon once again, and is the same as that used on the Atlas, and can be loaded with specialist munitions for other tasks. By comparison the Hellbringer gets a CSSRM6 that is essentially just like the SRM6, except there is none of this "well I missed and wasted ammo" or "I hit but only with one missile" malarkey, if you hit then every missile hits and if you miss then all the missiles miss.
Things are looking bad but its nothing yet....
>MG's
Both Mechs get two MG's. Same range and damage. But the Hellbringers are lighter of course.
And then we move on to
>Hellbringer only!
Because it can only get better amiright? No. The Hellbringer also carries four A-pods (essentially giant claymores) and a Antimissile system for point defence. And if that was not enough the Hellbringer also mounts a BAP to detect hidden units and pathfind, a ECM to provide that nice interference bubble, and the final nail in the coffin, a Clan Targeting Computer that really lets it bring the pain with precision.
Can the Warhammer recover?
>Armour
Both The Hellbringer has lighter armour, but even so the Warhammer's is nothing spectacular, although it does have the edge here. however this is offset by the fact that its opponent is pounding it with massive pinpoint damage groups at ranges it can only dream of.
>Speed
The Warhammer has a fairly average top speed of 6 hexes at a run. Compared to the Hellbringer that tops out at 8 hexes in a run, making it as fast (or faster in some cases) as most IS Medium Mechs, and completely outpacing the Warhammer.
>Cooling
The Warhammer should have the advantage here with its 18 heatsinks as opposed to the Hellbringers 13.... But the Warhammers are singles whilst the Hellbringer mounts doubles, easily out doing the IS mechs capability.
In conclusion the Hellbringer is faster than the Warhammer, whilst carrying superior (almost double) firepower and enough cooling to effectively use it whilst the fire control systems in it let the Hellbringer shred the IS Mech with highly accurate shots and the ECM and BAP add an extra depth to its defence. Armour is a noneissue as the Clan Mech hits hard enough to nullify the IS Mechs armour anyway.
And this is a Clan mech that is 5 tons lighter than the IS mech....
So, as you can see the Clans completely out power the IS Mechs, so in a one on one duel you will lose. But who said anything about 1v1? If you are fighting using BV then use that BV. Bring LRM carries and spotters, infantry platoons, pattons and scimitars, bulldogs and saladins. Hetzers are excellent when fitted with AC-10's. You have access to cheap units, use this. If you swarm them with fast units whilst your main line moves up, all the while keeping up a constant bombardment then you can destroy them. But one on one? Equal terms? Forget that, in material alone they will rape you like a snowman in hell. With those clank pilots vs your basic bod IS guy? Your a long metallic smear.