Thanks for the advice- I realize my newbness is showing (this is actually my first MMO period), and I find it hard to read some of the text at times. Totally missed the point about the Heroic quests being group-content: no wonder I wiped. Probably hitting the quest order in the wrong order as well: the dungeon I was in that I got slaughtered when two additional enemies jumped in was slogging, but a separate side quest was extremely easy.
I do the different blasters have different ranges, though? I'm not a sniper (yet), but one of the problems I've noticed is that I'm having trouble initiating combat from where there is good cover. I'm using a pistol now, but maybe that will go away once I get a rifle?
Blaster pistols and rifles have maximum ranges of 30 meters and no minimum range. Imperial Agents can pick the "Sniper" advanced class after level 10 (requires a conversation on either the Fleet or on the capital world, Dromund Kaas; you get the quest from a guy that shows up pretty much immediately after stepping off the elevator onto the main level of the Fleet), and one of the abilities that a Sniper can train extends range to 35 meters. The same is true of the reverse class, Smuggler; getting the Gunslinger advanced class can allow a Smuggler to shoot at enemies 35 meters away instead of 'just' 30.
Agents are designed to use blaster rifles primarily. Many of their abilities require rifles instead of other weapons. Once you get your advanced class, that may change. Snipers tend to use sniper rifles and Operatives tend to stick with blaster rifles. What's more important, however, is the main stat of the weapon and gear you're using. There are four main stats: Strength, Willpower, Cunning, and Aim. Any character gets small benefits from all of those stats, but the main stat provides the overwhelming majority of benefits. Warriors and Knights use Strength, Inquisitors and Consulars use Willpower, Agents and Smugglers use Cunning, and Hunters and Troopers use Aim. As an Agent, you should only use gear with Cunning on it - no Strength, Willpower, or Aim.
(The weapons system can be a bit goofy sometimes. Agents use blaster rifles and sniper rifles with Cunning on them. Hunters use blaster pistols with Aim on them. Smugglers use blaster pistols with Cunning on them, and Troopers can use blaster rifles with Aim on them. It's switched up between the two factions. So as an Agent, you may find blaster rifle drops with the wrong main stat, or gear with the correct main stat that happens to be a pistol. Don't bother with the other gear: stick to rifles with Cunning on them, and vendor the rest.)
The cover system can sometimes be a problem, but fortunately, before you get your advanced class, it's unnecessary. The advanced classes for the Agent are designed to go in two directions; Operatives are mostly melee/close-range damage and healers, and Snipers handle varieties of ranged damage. Operatives aren't really designed to use cover much. They rely on their mobility, getting around enemies for backstabs and whatnot. Snipers are the ones that are supposed to rely on cover. As such, only one of the abilities you get before you choose your advanced class requires cover: that's Snipe, and it's not necessary if you want good dps. You can play around with Shiv (melee damage) and your grenades (ranged) instead. So you're not tied to cover on Hutta if cover makes certain fights inconvenient.
If you pick Sniper as your advanced class, you can train an ability that allows you to take cover where you stand behind a little shield, instead of rolling to environmental cover. That'll solve any other cover-related problems you might have.