Laser-stars are war-spacecraft optimized to accommodate a huge laser weapon capable of eliminating an enemy thousands of kilometers away. They will usually have enormous radiators to deal with the waste-heat of their lasers and to cool the lasers further to reduce thermal lensing to keep the beam quality high. During an attack-run, they will use pulsed-beam lasers, but many laser designs can be switched between pulsed- beam and continuous-wave mode.
Missile Carriers are war-spacecraft optimized to shoot missiles at the enemy to kill them. The Rocinante from The Expanse could be considered a moderate missile carrier. An extreme missile carrier would be a propulsion bus whose only payload is hundreds or dozens of missiles.
With the relevant terms cleared up, on to the issue. Lasers have, unlike missiles (and kinetics, but the lines between those two are blurry at best in my setting), a limited range due to diffraction while missiles can just shut of their engines and go into cruise mode, possibly for centuries. This means that laser-stars will spend a long time on the approach doing nothing with their amazing lasers (they could threaten the enemy in Morse code with them, but that doesn't seem to be an effective use of a billion-dollar weapon system). Missile carriers likewise have their problems, or rather their missiles have. Unless you can install small, ridiculously efficient and powerful drives on the missiles, you either have to use humongous swarms to get through the point-defense grid (laser-star lasers, PDS-lasers, PDS-guns and defensive wide-angle-casaba-howitzers) our your attack won't be effective. Additionally, the enemy will know where the missiles will come from due to their very detectable drives. And all of this assumes that the missile carriers can get effective launches of before the laser-stars vaporize them. So essentially laser-stars will have a lot of ineffective downtime and missile carriers will be countered by point defense and the rocket equation.
My solution to these issues is based on the assumption that stealth in space is in fact possible (the links provide equations) (I know that a lot depends on the sensor nets available, but I assume that those will become worse as the war carries on as sensor hunters, x-ray fluorescent illumination searches, laser scans, and sandstorm kinetics will take their toll on them). I don't mean tactical Star Trek stealth but strategic detection lowering stealth. True, one can't hide a departure or launch burn but one can cool oneself down close to the temperature of the CMB with evaporative cooling and use metamaterials to make visible light and radio detection harder. If the cold missiles use serpentine rocket nozzles to strategically dump coolant to maneuver, the enemy will know only that there is a missile coming in and that it is somewhere in a 10 million square-kilometer zone. Useful information to be sure, but virtually useless to the point-defense effort. When the missiles will inevitably be detected they might have gotten into the range where they could effectively deploy their payload, say a nuclear-pumped x-ray laser.
My solution to the issues of laser-stars and missile carriers is to use the laser-stars laser to accelerate missiles until it can effectively fire at the enemy. This is the concept of laser propulsion. I could either use laser sails or laser thermal rockets. The delta-v budget of the laser-boosted stage of the is given by:
$$v = sqrt(d / 0.5 * a) * a$$
$v$ = change of missile velocity relative to laser-star
$d$ = distance over which the missile is accelerated (effective range of laser)
$a$ = acceleration of missile
According to my research $a$ will be several G's or even several tens of G's and $d$ will be in the hundreds or thousands of kilometers, resulting in delta-v budgets of several tens of kilometers per second. After the laser burn, the hot propulsion stage is ditched and broken up in a wide field shrapnel storm meant to harass the enemy. The cold and stealthy missile continues to cool itself and uses the coolant to increase the volume of space where it could be.
The warhead the missile will carry if they are used in an anti-spacecraft capacity are very diverse.
- kinetic impactors (nuclear gun, kinetic missile, cold bullet)
- sandstorm kinetics (small particles meant to damage surface structures)
- directed energy (casaba howitzers and bomb pumped lasers)
- virus bots (micro-machines meant to land and hack into enemy computers)
- combat drone (the closest thing to a space-fighter in my universe, various applications)
In the end, assuming that my assumptions about warheads and the nature of stealth in space are correct, is it thus reasonable to conclude that a laser dominated battlefield will automatically lead to a missile dominated one?