I'm guessing the OP hasn't gotten very far in the game, if hes complaining about black magic spells 1 shotting people (especially the rank 1 spells). Further in the game it becomes more about knowing which class to send vs which opponent, which one to keep back to support your team, effective ways to keep the enemies from your "quickest to die" units. In the beginning, you don't have many of those options. You just charge in, and when the dust settles, you make sure you dont have any serious casualties and you move on
Tactics Ogre is great, dont get me wrong. It does rank as one of my favorite games of all time, also my #2 favorite strategy game, right behind Tactics. But the problem with TO is its lack of customization of units. You can make a dragoon, yes. He fights dragons well and has some weak support magic (if I remember correct). But, can you make a Dragoon with the ability to steal, as well as jump an infinite height and use a healing potion every time he gets hit? or maybe give him the ability to block all incoming melee attacks, or even cast Reraise on himself when he takes dmg? Not in TO
Edit: On the other hand, I do wish FFT had used TOs style of game progression, in that you pick a side of a conflict, and the game changes its course depending on what you choose, ending with several different paths through the game...
Anyways, back on topic. Ending Chapter 1, I always like to have a summoner, huge help in the battle against Algus. If you are still having trouble getting past him, equip Ramza and Delita with Auto Potion and your problems should be solved. Personally, if you have a team of Ramza (as squire, monk or knight even), a Monk, Summoner, and a Mage of any type, as long as they have some White Magic primary or seconday skill so they can heal, you should be ok. Put the monk and healer-mage away from Ramza, to take out the knight+black mage that are close to them at start. The two of them should have no trouble taking care of themselves.
On the other side of the battle, keep your summoner back until the knights+algus+mages bunch up in some way, by using an auto-potion'd Ramza as bait. Once they are grouped up on him, bring in Summoner with a spell of Titan or better. Should take out the mages and severely weaken the knights at least.