The Paragon works because of range and sheer Flux Capacity / Shield Efficiency; its System is pretty lousy and unintuitive to use, but it gets away with it, since players will hardly ever use it and find out how (really) bad it is (if it basically conferred immunity, didn't put Hard Flux on the ship and let the Hard Flux drain happen, it'd be all right- as it stands, when the System goes up and it's taking fire, it's losing the Flux war even faster than if it kept firing). In Vanilla, the Paragon works unless it gets mobbed by Destoyers and Frigates that can use Kinetics- this will beat it every time. I don't fear Paragons in Vanilla, given that I tend to go for a mixed-arms approach and almost totally eschew High Tech.
The Odyssey is kind of a poster-child for the way that all-Energy can only work if given a huge advantage via stats or System or other things, given the balance issues.
This is totally fixable. I'm playing a pretty viable, roughly balanced version of the Odyssey right now.
The balanced Odyssey has an efficient shield, better overall Flux stats so that it can fire without running out of room if given reasonably-efficient weapons (i.e., Dissipation > Weapon Flux, by more than enough to afford to spend Soft Flux draining Hard Flux with the Skill; if maxed on Dissipation and kitted out well, the ratio's about 1.5:1). This makes it able to shield-tank long enough to stay in a scrum (it still has relatively-poor Armor values, so it doesn't like dropping shields).
Its System is High Energy Focus, which has been rebalanced so that it improves damage enough to matter. It also has turret arcs that are sensible; at an angle, on one side, it can bring all three Large Energy turrets to bear., and can usually bring two to bear, rather than the current situation, where there's barely any functional overlap.
It also is using the rebalanced Energy weapons, which have, at this point, completely different stat-lines, other than OP costs. In general, I found Energy was the most difficult damage type to get balanced well, but it's generally functional now. Most Energy weapons had to trade a bit of accuracy or total DPS to get their Flux efficiency into a range where they were solid.
Even in my build, though, and even with my current iteration of weapon rebalance, it can't use an all-Beam build; it's slow enough that it has to alpha small stuff that gets close enough to put Kinetics on it and gradual kills with Beams aren't viable. But my favorite builds for it often have Beams in supportive roles or as defensive weapons, and a level-29 Captain running an optimized Odyssey can be expected to wreck things very reliably and shield-tanks well enough to avoid being destroyed by anything less than a mob or an Onslaught / Conquest geared for shield-kill. I think that's how it's supposed to work; the Odyssey should feel like it's the inverse of the Paragon- shorter-ranged, faster, more built for alpha, but more fragile.
So it's the result of a lot of work on different areas. But in the main, it's largely down to having Energy weapons and Beams be balanced properly, which requires examining the rest of the stuff as well. This is key; otherwise the only way to make High Tech / Energy builds viable is to give them ridiculously-OP Systems or other crutches.
On specific weapons:
The Tachyon Lance is better than the HIL in Vanilla, but only because of the scripted effect and scary range on the Paragon. I don't think it's worth mounting on anything but a Paragon right now; the burst damage isn't great and it's only cool against targets with small shields whose Flux levels are already high.
The HIL is still pretty bad; it barely outperforms a Heavy Mauler for OP costs, yet takes a Large Energy slot... and that's just the surface numbers.
If you look at the details, it doesn't at out-perform it, when we consider that it doesn't inflict Hard Flux and that, unlike the Heavy Mauler, it's artificially gimped vs. Armor (it does a mere 16.7 damage per tick against Armor, before the Armor reduction, after the hidden Beam nerf in Settings).
So we're talking about a weapon that can fry Fighters and small unshielded Pirate trash, mainly, at a horrific cost for its efficiency, not exactly a world-changer. I'm sure that looks impressive to people, given that it was useless before, but it's not actually good.
The HIL should be considerably more Flux-efficient than it is, if that's where the damage is set and it's going to keep that damage type. To put it another way... in Rebal, after getting rid of the hidden Beam nerf, it's at 400 DPS / 235 Flux and is Kinetic, yet it's still not amazingly powerful, it's merely competent as a Flux-trader at that point, when Soft Flux is considered properly.
The Guardian still underperforms against every other PD in the game. I'd need to double-check, but I'm pretty sure it's even worse per OP spent than the Mining Laser, lol.
In Rebal, it got moved to Medium, range was set to 900, DPS/Flux is 2:1... and it's now effective on ships that actually want high-end PD and are willing to spend 15 OPs on it; it does 150 a strike, so it can efficiently kill Harpoons, but it can't stop swarms of Reapers or even mass Annihilators (due to re-engagement times) and it's not an effective offensive weapon, since it's still Energy and Soft Flux and therefore remains a poor Flux-trader (2:1 Soft Flux Energy damage is worse than 1:1 Hard Flux from anything; this isn't a Light Needler, performance-wise).
So, yeah. Odyssey's problems are many and none of the Large Energy Slot Beams are tuned well yet, in Vanilla. But I really didn't start this post to talk much about those weapons, frankly; there are so few ships that can even mount them, they're almost a separate problem (well, other than all the modded stuff out there that probably has suffered, balance-wise, by using Vanilla's numbers as a rough guide). I'm much more interested in the mid-to-lower end of those things, where I feel like there are some basic fixes available that would help them out. The big Beams aren't seen all over the game, after all, whereas stuff like the Graviton Beam, Phase Lance, etc. should be seen pretty often, but are largely a waste of OPs.