Deep scars and low morale remain among the American diplomats here who survived the sacking of the U.S. Embassy by a Pakistani mob in November.

One diplomat has frequent nightmares about the five hours he spent trapped in the embassy vault while fire raged around and gangs of Pakistanis shot rifles down the ventilator shafts. "I have to call on all my professional training to remain emotionally detached" when dealing officially with Pakistanis now, the diplomat said.

But soon only a handful of more than 100 Americans who survived the embassy attack, which killed two Americans and two Pakistani employes, will still be here.

The rest will have followed their evacuated families and taken their expertise and their language capabilities back to Washington or to another assignment, taking advantage of a compassionate quick-transfer policy adopted by the State Department as the answer to the plunging morale here.

Pakistan is only one of several key countries in the so-called crescent of crisis in the southwestern Asia where, in reponse to attacks here and in Tehran, families have been evacuated and mission staffs dramatically cut. Paradoxically this has come just as the United States says these areas have become the number one foreign policy problem, in need of expert attention.

Throughout the region, in crucial countries such as Pakistan and Saudi Arabia, the evacuations and cutbacks have made it increasingly difficult to get top Foreign Service officers to serve. The result, State Department sources in the region and in Washington say, is a clear dropoff in the quality of embassy reporting and representational activities.

Reports from Persian Gulf countries indicate that American diplomats there also are upset by the orders from Washington that diplomats' wives and other dependents leave the area.

Some diplomats in the gulf are said to believe that Washington overreacted in its estimation of danger to U.S. personnel there. Although the area is strongly Moslem, there have been no reports of any significant unrest such as the riot here and an attack on the U.S. Embassy in Tripoli, Libya.

One U.S. diplomat in the gulf said that the original directive from Washington called for evacuatin only of dependents who volunteered to leave. But when only a few volunteers came forward, he said, the embassy received a message making it clear that most families were expected to "volunteer" for departure.

It is quiet now at the burned-out bhulk of what used to be the American embassy here. Only a pile of twisted steel lies outside its walls as a grim reminder of the attack.

The Pakistani government has promised to pay for the reconstruction, as required by international law, and a team of American engineers has decided that the embassy can be renovated without starting from scratch. U.S. officials here speak of being back in the embassy building in two years. u

While on the surface it looks as if the mob violence and Pakistan's failure to protect the embassy or to rescue those trapped inside has been forgiven and forgotten, scars remain among the American survivors.

The embassy here suffers from low morale -- a sharp change from the days not long ago when Islamabad was considered one of the best assignments in the Foreign Service. It was thought of as a place that might be slightly dull but one that was safe. It had a good international school and was a good place to raise a family.

That is all changed now.

Much of the reason for the low morale is the family breakups caused by the sudden evacuation of dependents after the embassy burning. According to diplomats who remained here, this has put strains on the children, who had to start new schools in the middle of the terms, and on spouses, who have to set up housekeeping alone in the United States.

The separations have made for wretchedly lonely men here, many of whom are taking advantage of the State Department offer to transfer them before their tour in Pakistan is up. By summer, only a handful of survivors of the embassy burning will still be here and most of the newcomers will be bachelors.

This has good and bad sides. It will prevent U.S. diplomacy here from being soured by even the residual bad taste that many of the survivors feel toward the Pakistanis. But it will also deprive the embassy of some continuity, especially important now since all its files were destroyed when the embassy was burned.

But there appear to be reasons other than family dislocation for the low morale here.

Embassy employes talk openly of their feeling that the Carter administration dealt far too kindly with the Pakistani government over the embassy burning -- starting with the profuse thanks President Carter gave Pakistan for help in rescuing those trapped in the vault, when in fact they got themselves out after dark when the mob left. The Pakistani Army watched as the Americans climbed down through the flames from the embassy roof.

The American's feelins are also apparent from comments made during showing here of a television documentary, "Dying to Be a Diplomat," which is one of the big hits on the American Club video tape recorder. The program about violence against U.S. embassies and including long segments on the burning here, is screened once or twice a night to rapt audiences.

During many of the showings, catcalls greet the comments of State Department spokesmen while the program's narrator is cheered when he emphasizes how long it took the Pakistani Army to respond.

Meanwhile, the embassy is functioning in a building that was fully occupied by the U.S. aid mission before that program was cut a year ago. The facilities, intended to be turned over to the United Nations were taken over the day after the embassy was destroyed.

At first the embassy here was completely without radio and coding equipment. But within 48 hours an emergency kit was shipped in and by now the diplomats have the same secure communications they had before the attack.

It took a hundred workers two months to clean out the inside of the embassy building, pulling out charred and twisted desks, tables, chairs and files. Most of it has already been hauled away and sold for scrap.

Still remaining, however, are the completely burned cars in the motor pool -- both official embassy vehicles and those belonging to American workers.

The burned-out cars have created another nagging problem for Americans here. The Pakistani government allows diplomats to import only two cars duty free, and owners of the burned cars must have special dispensation to bring in replacements. So far the government has not acted, but embassy officials say the bureaucratic wheels grind slowly here.