The dominix has an awesome bonus to drone optimal range. If you combine this with any sentry that is not a garde you have incredible range projection (you just need to use the right damage type as you are no longer using the top DPS drone). You can theoretically push a curator into hitting above 100km, which is the 3rd shortest range drone.

With that in mind, you really do not have to fit an incredible tank and you can still not have much of a concern of blowing up. How to do this? - May I point you toward the MJD.

[Dominix, New Setup 3]
Large Armor Repairer II
Armor EM Hardener II
Armor Thermic Hardener II
Co-Processor II
Drone Damage Amplifier II
Drone Damage Amplifier II
Drone Damage Amplifier II

Large Micro Jump Drive
Prototype 100MN Microwarpdrive I
Sensor Booster II, Targeting Range Script
Omnidirectional Tracking Link II
Omnidirectional Tracking Link II

Dual 250mm Railgun II, Spike L
Dual 250mm Railgun II, Spike L
Dual 250mm Railgun II, Spike L
Dual 250mm Railgun II, Spike L
Drone Link Augmentor I
Drone Link Augmentor I

Large Drone Scope Chip I
Large Sentry Damage Augmentor I
Large Auxiliary Nano Pump I

Bouncer II x5

If you just start out doing L4s in a Domi and safety is your primary concern, you might consider fitting 2 Large Armor Reppers and a couple of Cap Rechargers. That should give you enough tank for virtually anything that could go wrong. Just don-¦t perma-run both them
In fact, consider the second one purely an emergency system.

Once you are comfortable with running L4s and find that you don-¦t need the second LAR, switch it out (as well as a few of the cap rechargers) for more damage mods. Something like the fits listed above.
DPS tank best tank, after all.

Also, a Domi (or Navy Domi) can be shield fitted too for awesome DPS but that requires very goods skills.

sentry do instant damage, where heavy combat drones are slow and have to travel between targets.
tank fit it rat specific else u need a higher slot amount for tank in my experience.
guns meta 4 and u wont need to switch them normaly.
t2 in tank is the most important i would say. but weapon support is directly afterwards.

Yep, that's right, drones don't require ammo. Neither do T1 lasers. This is why Amarr drone ships are very cost effective.

Usually, on a dedicated drone boat (which is, like, 90% of everything I own) I'll use that extra high slot for a small/medium remote armor repair module. That way I don't even have to pay for my drone repairs, and I can repair them between rooms without having to dock-up first.

Yeah, I'm that cheap.

The benefit of sentry is - they draw more damage and they own more tank.
Here is a discussion regarding Heavy drones vs. sentry drones: https://forums.eveonline.com/default.aspx?g=posts&t=33050

But - to survive Level 4 missions is not only a thing of tank and damage!
You can do Level 4's in a Battlecruiser, of you know how to handle the mission...

So to know about the mission, which resistances to fit, which ammo to load, which ship is Trigger for the next wave of NPC -
this is the way to survive. Even in a ship which is fitted with T1 stuff.
Refer to this site for detailed Information about each mission: Eve Survival
The name of the site says all...

my personal opinion to that fitting is its pretty bad. I linked a domi fit i would prefer before. But to get it straight your drone control range is to low (with Electronic Warfare Drone Interfacing 5 only 100km). Get rid of your guns (only fit them when u have spare) and fit more dla. I would max use 1 flight of small drones rest sentries because Domi is specced for sentries.

EDIT: i stated my personal opinion u can ofcourse fly it anyway u like and u feel good with it ^^

One of the best things about eve is discovering how to fit your ship, mainly through trial and error. It also depends on your tactics.

I wouldn't put both a MJD and a MWD on the domi because you can pretty much MJD up to safety then MJD straight to the gate (bearing in mind its 2 mins until you can use it again). Thats what I do in DED complexes.

With sentries (when you get them) you will need Omni Directional links to make sure you can hit stuff so you don't really need the Cap Rechargers. You will have to manage the cap carefully, the range tank you get with a domi reduces the ammount of damage you receive.

In the Lows I use damage specific armour Hardeners which you can change depending on the rats you are facing.

Even though you can't use tech 2 yet, meta 4 modules are probably the most useful for you.

remember to use the compare tool for any mods you are unsure of, there are some surprising examples where the lower meta modules are better and cheaper than their t2 counterparts, there's a sticky devoted to listing them in ships & modules.

neocom panel on the left ,
i think it starts life near the bottom if you haven't moved stuff around
when you click on it, you get a tab with two pretty empty (baring some prompt txt) windows,
drag module icons (ccp are making this possible from almost anywhere in the ui) into the window on the right you can compare a number of modules by any attributes they share.
you can use this to get some surprisingly good fits out of relatively cheap modules.
its also great for finding which faction mods are actually worth using and which are for magpies.

Edit: seriously, finding this thing was a MASSIVE help for my ability to fit ships.
it should also save you a fair bit of isk,time and effort